A lot of the rock the makes up the higher peaks in the southern Catskills (around Slide Mtn., etc.) is actually really high quality sandstone that seems like it could make for some good climbing. Unfortunately, there seem to be very few outcroppings of this good rock; the major cliffs in the Catskills seem to be water cut cliffs at lower elevations in the shale.
I spent some time working in the Catskills a while back and managed to find a handful of nice boulder problems on the sandstone, but these were all very scattered around on medium sized boulders and the occasional short outcropping. The style is like Castle Rock (Bay Area, CA), or the deep South.
There is probably a small stash of decent bouldering on good sandstone somewhere in the Catskills, but I doubt that it is enough to make a destination out of. It would probably be a long hike/bushwack to get to, so I doubt that it would be worth it to seek it out, especially with much better options nearby at the Gunks. In terms of cliffs for roped climbing on good rock, I doubt that there is much to be found in the Catskills. The ice, of course, if a different story.
The best potential for good new rock in NY, though, is in the Adks. Even the well-traveled crags around Keene Valley and the High Peaks are far from being fully developed, and the southern Adks are still quite underdeveloped. It is quite telling that many of the best routes, even in Keene Valley and the High Peaks, have gone up in the last 10 years. Routes like Freeride (Wallface), the Direct South Face on Gothics, My Generation (Hurricane Crag), much of the Typhoon Wall (beneath Hurricane Crag), and many others come to mind. If these routes- on some of the better known and more visible cliffs in the area- were unclimbed as of 2000, there must be a lot left out there. Silver Lake, of course, is another major frontier just now being tapped.
I think that the next frontier for Adk climbing might lie in large-scale, Squamish-style cleaning and unearthing of vegetated cliffs. There are some steep and potentially appealing cliffs in the Adks that have been left mostly untouched because they have been dismissed as being too dirty; climbers (understandably) passed them by in favor of cleaner cliffs. Having seen some of the great climbs that have been dug out of the moss in BC and western Washington, though, it makes me wonder what could be found in the Dacks if more aggressive cleaning is accepted and embraced. I think the Freeride (Wallface) was one new-school route in the Adirondacks that was unearthed due to some heavy cleaning on rappel; it is a fantastic route.
Anyway, my apologies for the tangent from the original topic.