Road: Mt Loop and rd 49 had plenty of potholes but would seemingly be passable with a standard vehicle. 

Trail starts off with nice swooping switchbacks the first 1.5 miles or so before throwing elevation to the wind and just doing the typical N Cascade crawl and heading steeply up. Some downed trees easily enough maneuvered. I was not personally harassed by bees (or hornets, or wasps), though there is a silver, dead (ghost) tree after Bingley gap on the corner of one of the tight switchbacks that contain a fine denizen what looks like hornets living in the hallowed out space. They let me pass peacefully. Sorry I did not get a waypoint, just don’t lean against any dead trees whilst catching your breath. 
At the top of the ridge before dropping down to the lake the trail again starts out with a lovely long and swooping tread, drawing one in, with promises of ease, however, it quickly turns into an unmaintained billy goat of a trail that is easy to follow. I did not see anything sketchy, though it could be I took a different route than a previous trip goer. 
I did not see bear, cougar, or anything resembling a bipedal-oid, including Bigfoot. I did see lots of grouse, swallows, toads, trout, a plethora of pollinators of all shapes, and the usual regular suspects. 
Biting flies were only bad in the forest area if you stopped for too long, mosquitoes were present but actually not too bad. The evening there was a cool breeze which helped, and the morning found a few joining (eating) me for breakfast, but I tried out my new thermocell and am cautiously optimistic that it was useful. 
As an fyi, there is a backwoods toilet. Cross the stream outlet and veer to the left, where you’ll find a campsite with a trail that continues through. You’ll see a sign. It is a nice toilet, but I suspect there are a few people who have visited who did not realize it was there. LNT. 

This is a wonderful, albeit strenuous hike that is equal parts challenging and rewarding. Miles 1-3 are thigh pulverizers, and the trail intermittently throws you obstacles in the form of fallen logs and exposed roots that require some dexterity to pass. However, besides some narrow passages and brush this trail was well maintained and easy to navigate. Only saw two people on a Sunday. Start early and earn the reward (and solitude) while the more popular trails are packed with families. 

Download directions and map. You will loose cell at gravel road.

Trail can be tricky as you exit the forest to find lake.
First Y in road, left.
Second Y, left.
Then when you are going down to lake, you will come to a marsh, some people might think it's a water crossing. It looks like there's a very clear trail straight ahead, it is not the right way. Stay right. You will see the trail. Just walk along the marsh straight towards the lake.
There is a hidden privy though, if you do go straight, at bottom on hike by lake, it takes you a little bushwacking through the woods where you will find a privy that not many people probably won't exist.

Overall great butt kicking hike with a fun refreshing lake at the end.
Clocked 11.5 miles with 1/4 mile privy hunt when went the wrong way by the lake.

We backpacked the Lost Creek Ridge trail to Lake Byrne in 3 days/2 nights. This scenic, lightly trafficked trail has been on my to-do list for a while. Happy we finally got out there! This trail exceeded expectations on beauty, solitude, and, most importantly, difficulty. Steep grades, relentless elevation gains/losses, sustained washed out sections with loose tread, and minimal water sources made this one of the hardest backpacking trips I've done in Washington. It was very similar to the Skyline Ridge trail in ONP. All that being said – it was definitely worth it!

Day 1: Lost Creek Ridge TH > Round Lake. We opted to split the hike out to Lake Byrne with a night hike out to Round Lake. Hiking under the stars is a delight – great way to avoid the heat and other people. Lots of switchbacks up to the ridge. Unsurprisingly, we were the only ones on trail this evening. Once you're ~0.5 miles in, there's no water the rest of the way up the ridge. Round Lake is the first water source, but it's a significant detour (and a big descent) off the main trail if you're not planning on camping there. There's a washed-out section on loose dirt with a rather unfavorable runout at the beginning of the spur trail to Round Lake. This section is passable, but was pretty sketchy at night (and only slightly less sketchy the following morning). Round Lake is beautiful! Great star gazing. We clocked 5.5 miles with 3,500 ft of gain, taking us around 3 hours.

Day 2: Round Lake > Lake Byrne. Mosquitoes were out in force in the morning. We had a good warm up ascending the trail from Round Lake to the ridge. The trail from Round Lake to Lake Byrne is not easy. Flat/mildly graded sections of trail are minimal. As soon as the trail gains any elevation it takes you right back down, and vice-versa. Over, and over, and over again. Very difficult to hike faster than 2 miles/hr on this section. The grades are steep and the tread is loose. But the views are incredible, and you'll encounter very few other hikers (I think we passed 5 other people all day, all headed in the opposite direction). Water is minimal on this stretch as well. There are some small streams between Round Lake and Camp Lake - the last one is about 4 miles before Camp Lake. I imagine these will mostly dry up by September. You will also pass Hardtack Lake on your way to Camp Lake, but it’s a detour off the main route. Camp lake was beautiful and cold, but made for a refreshing swim and water fill. Plenty of space to camp around there. You’ll hit Lake Byrne 1 mile past Camp Lake after passing through Little Siberia, which has some lingering snow. Plenty of camping options at Lake Byrne as well. We saw only one other group camping there. Fun trails to explore around the lake, and excellent views of Glacier Peak. Lake Byrne was much warmer than Camp Lake – so nice for swimming! Lots of mosquitoes here as well. We clocked 7.3 miles with 2,900 feet of gain along this stretch taking us around 3.5 hours.

Day 3: Lake Byrne > Lost Creek Ridge TH. The elevation on the hike back to the trailhead didn’t feel any easier than on the way in. Start early to avoid the heat, and fill up your water wherever you can. We didn’t pass anyone until we were within 3 miles of the trailhead. There’s also a bee’s nest on the trail around this point which we unfortunately did not escape unscathed. We moved pretty quickly on the switch backs down from Bingley Gap (about 3.3 miles/hr), but our legs were definitely feeling the sustained downhill by the end. Stats for the return trip amounted to 11.6 miles with 2,400 feet of gain taking us just under 5 hours.

This was an incredible trip, well worth the anticipation and effort. Don’t let the mileage/elevation stats fool you – this is a hard trail! Definitely one for seasoned backpackers who enjoy type 2 fun. You could totally do this trip in 2 days/1 night, it would just leave you less time to enjoy all the splendor.

This was my first solo hike, as well as my first overnight hike and hike over 10 miles roundtrip and due to my work schedule, I got to the trailhead at 19:50 Friday and nobody had been on the trail for at least a few days. You are alone.

Drive has potholes aplenty, be careful (one was 2 feet deep, marked with several branches sticking out of it).

The first 3.5 miles are quite punishing, almost like a staircase at points, something I was equipped for, but was out of shape. I stopped to eat around 22:30 and got back on the trail about 23:15. After hiking up the trail about 20 yards, I found a mountain lion hiding under a log, probably waiting for me to finish eating and leave to see if I'd leave anything behind. I fell back screaming in the dark and fired one shot into the sky, scared out of my wits. It ran off. I got back on the trail and hiked another mile. Hiking in the dark is hard on this trail, as it is as narrow as 12 inches in places and the grade in many parts has to be around 90 to 100 on the fall off next to you. Spookier still in the dark, your steps in front of you are uncertain and the ones behind you seem to disappear. You are alone.

I collapsed to sleep at around 01:00.

It was supposed to be a rolling thunderstorm into the evening and break around 11:00 Saturday, but it was clear the whole time. In my tent, I was freezing. I forgot to pack a pad to sleep on, so the ground sapped my body heat for the three hours I slept. I woke up at 04:30 and started hiking again.

I came to a split in the trail around the 4.5 mile marker. I did not pay attention to the map at the trailhead and there were no signs, so I didn't know which way to go. I went right and flat. I packed in 2 quart canteens full of water and ran out around 5:45. There's a couple creeks and streams on this second path (I later found out was Camp Lake trail) that you can refill at. Beautiful view at this point onward, since you're no longer hiking switchback after switchback up the mountain, but rather up upon the ridge. The clouds expand for what feels like eternity. You are alone.

After hiking around 3 miles past the turn, I realized I hiked all the way around to the south side of Round Lake and was heading towards Camp Lake trail. It was 07:28. I turned around and went back to the split, heading up 50 yards of incline to find Round Lake. Beautiful view of a lake viewed by only a handful of people in this vast state and fewer abroad.

Hiked back with no problem, enjoyed my last meal at the car at the trailhead, passing three separate groups of hikers on the way. Its isolated enough nobody broke into my car. Nice stuff. I do not recommend taking pictures. They don't capture the beauty of this place.

10/10 will come back.