Thanks for the info. I might try to get up Whitney next week and if so, I'll take a good look at Muir while I'm there. I'm fairly confident I could safely climb it, not so sure about down climbing it. So I'll wait and tag along with someone else.............................................DUG
Muir is a tricky bit of rock-work. I'm of the opinion that it firmly crosses into the realm of Class 4.
Here are two potential routes as seen in one of jdmorris's photos on summitpost:
(The route in blue is purported to be closer to class 3 and the red deviation is class 4)
Tyndall is good, from Shepherds Pass your entire route is in view and apparent.
(Courtesy Pebblecrawler's Blogspot)
Crossing the Williamson Bowl is something of a chore and getting in view of the correct ascent chute is crucial. Make sure you do your homework Piero Scaruffi gives a good idea of the route:
http://www.scaruffi.com/travel/williams.html