I've been up to the base of the class 4 section on Sill via the North Fork of the Big Pine trail/Sam Mack Meadow/Glacier Notch/L-couloir. It is a beautiful approach hike, but long. Once you get to the toe of the glacier above Sam Mack Meadow the traverse along the morraine to Glacier Notch is perhaps the most tedious boulder hopping I have done in the Sierra (especially on the way back down when you are snookered). Then the chute up to Glacier Notch was perhaps the sketchiest chute I have enountered, with the group above us knocking down a rain of rockfall that would have been deadly had one been in there. Once they cleared we proceeded up with no further issues. The climb up to the L-couloir is not bad, but then the class 4 traverse to the summit ridge ended up turning me and my partner back. This was early in my climbing/mountaineering days and I simply wasn't mentally prepared for the exposure. If I were to encounter that stretch now I feel confident it would be relatively straightforward, though certianly worthy of close attention (I have since done Mt. Russell East Ridge and Laurel Mt northeast gulley; I feel Russell East Ridge has similar exposure over a much longer strech, and Laurel required much more technical climbing).
With that said, when I go back to knock off Sill I will likely go via Bishop Pass/Potluck Pass/Southwest slopes. It is longer, but not that much longer. And from what I have read about that route there is nothing on the west side worse than the morraine traverse/glacier notch chute. My reasoning for doing this route would be to see a different area of the Sierra, and have more confidence in the descent/downclimb.
I would be interested in teaming up next summer if you choose to hit Sill and need a partner. My preference would be to go via Bishop Pass/Southwest slopes.
