I'd say Sunapee isn't particularly challenging. Interesting, yes. Challenging, I wouldn't say so. There are a couple of steepish runs, and some bumps here and there, but for that matter there's a steepish run at Crotched, which bumps up and gets icy.
This is one of those threads that disappear down the minutia wormhole!
Sunapee has decent glades, one glade is steep, only skied it once. I forgot where it was... somewhere near the high speed quad area. I was with a group of friends and family, if I was skiing by myself, I would lap that trail. Southern NH doesn't have many storm in consecutive order so a natural base doesn't form, I can understand why ski patrol would close some of the steeper sections. Having said that, the glades in crotched doesn't compare, however I heard that they did open some new glades that has some pitch, just never skied it yet.