I climbed Mt. Sill in early August of 2005. The 8 mile hike up to Elinore Lake was absolutely beautiful. It starts at the South Fork TH on the Glacier Lodge Road in Big Pine, CA.
Most of the hike to base camp (Elinore Lake) is high and dry. But after passing Willow Lake, the mosquitos became almost unbearable. Wear long sleeves.
As for the actual climb on Mt Sill, it's one of the best I've done. It's extremely challenging. Almost too challenging to try as a solo ascent. The guidebooks I've read on the East Couloir depict it as a class 3 climb. However, the bergschrund I encountered in August was enormous. I skirted around and climbed up a 4th class route to the right of the couloir and envisioned a sketchy descent on the way back down. So once I got passed the 4th class stuff, there was quite a bit of excellent 3rd class cruising. FUN.
The view from the summit was spectacular. On the way down, I decided to take the right fork (climber's perspective) of the East Couloir that I thought might help me avoid a 4th class descent. I was mainly worried because I didn't have a rope, or a climbing partner. Bad news: the right fork of the East Couloir is more like 5th class (about 5.7+), which was way more sketchy than a 4th class descent. Good news: I'll never climb alone again. I got stuck on the right fork's icy couloir right before the bergschrund drop of 30 vertical feet and a 15 foot horizontal gap to the Sill Glacier. So I used a sling to tie off a knob on the adjacent rock and aid myself down to a 3 inch ledge. From there, the 5.7 downclimb was nerve-racking and exhilirating. I managed to find a narrow ledge to jump off to get myself back down to the Sill Glacier and back on the cruiser path towards Elinore Lake.
In a nutshell, this climb is well worth the time if you have a partner, but then again, if you have a climbing partner, you might want to just do the Swiss Arete route up Mt. Sill.