Twin Sisters is popular enough that the snow on the trail is packed by the traffic. I was able to walk up the trail without snowshoes even though the snow was up to a foot deep off of the trail. The packed snow is slick enough that trekking poles are pretty much required to help with staying upright. Gaiters are also a really good idea, especially in late afternoon when the sun can melt the top layer of snow into mush. This is in late November during a warm, sunny day.
The only postholing was on the summer road while walking to the trailhead from the Lily Lake visitor center, and in a few spots just below the timberline. Above timberline, the wind keeps the terrain pretty clear of snow.
Twin Sisters also offers lots of technical rock climbing. The northern part of the mountain has a several large rock buttresses that can be seen from Estes Park. This is known as the Crags and offers some excellent multipitch trad climbing. The area isn't visited very often which does not reflect on the quality but more on the approach. There are several approaches but no road side cragging here. Both of the local guide books do an excellent job of covering most of these routes which were put up in the 70's and 80's. Don't expect an bolts, maybe some pitons but do expect some dicey gear and sandbag ratings.
Nice concise page, but with a good amount of info.
These are purely suggestions:
1) It might be nice to use a photo of Twin Sisters itself for the main photo for the page.
2) It might be a good idea to state that in "winter", one must park by Lily Lake, as the road up to the trailhead is closed. Winter means until the snow is gone (it was still closed yesterday, April 28.)
Thanks for doing this page!