that guy hikealongpete posts videos of the trail over on the WPS site...(maybe here too, I dunno). I found them helpful for knowing what to expect. I can only watch the 3X speed versions though. The realtime versions are just too dang slow to keep my attention.

The relevent segments for Mirror Lake would be:

4MW3X
http://www.youtube.com/watch?v=zsOA2zT_0VA
5MW3X
http://www.youtube.com/watch?v=wxhXFaDmQBk