Went up to Mount Defiance via Mason Lake today -- no real issues to report except that due to the storm yesterday, leaving everything pretty soggy, and the amount of brush that grows over portions of the trail, my legs got soaked (of course this had to be the one time I leave the Gore pants at home). Oh well, the sun poked out about half the time while I was on top, and dried me out pretty quick. Decent views from what I could see; clouds obscured anything more than a valley or two away.
Be sure to take the left fork a little over a mile out from the trailhead, and stay on the trail (which winds through a very pretty, thickly moss-covered hemlock grove along the creek) for as long as possible. The trail starts to parallel a big field of granite boulders on the right, and eventually the trail ends near the top of that field, at which point you must scramble across. You should be able to see some pink flagging tied to a sign at the top of the boulder field, marking the continuation of the trail to Mason Lake. On the way down, I saw lots of people unnecessarily crawling up the entire boulder field when there is a perfectly good trail just 50 feet to the side. The sign with the flagging instructs you to follow the cairns to get back down -- I think you want to ignore this as the cairns seem to continue all the way down the length of the boulder field. Very misleading if you ask me. If you're not up for the adventure, just go back the way you came.