Lynnbern, Last fall I climbed the MR and took a series of videos at all the tighter spots. They are available in three separate threads, starting here: Mountaineers Route videos: North Fork to Upper Boy Scout Lk

Also, the first paragraph in the Orientation Notes (link in the box to the left) has a link to: Mountaineer's Route info links within...

All that info will give you a pretty good idea. The MR is definitely more challenging than the main trail, so if someone was overcome by conditions there, the MR is not a good idea.