Mostly level design, some game. Environment design is mostly artist territory here, where they can make the materials and models they need to fill a space. I share a quad cube with 3 artists and they're pretty cool and wacky. I'd love to post something where I can answer questions / whatnot but I don't think I've been here long enough to be of any help to anyone.
I've been so used to Radiant for the past half a year that I shudder thinking of how terribly my Hammer skills have degraded.
You should do something here. I'm probably not the only person who has questions.