I like GameMaker Studio a lot! It's super useful as a solo-programmer but I'm not sure it shines in group projects. I use the 1.4999 version because I'm a little set in my ways. I don't know how GMS2 is with 3d or 2.5d games but 1.x Game Maker stops short of Doom in terms of 3D capabilities. Would absolutely recommend it for 2D projects though!
I'm a self taught programmer (English major haha) and I'm trying to expand my knowledge base a little bit. I think Unity is the next thing I'd like to learn but I've never done a "real" programming language before!