welcome!
i'm a full time c/c++ dev in the windows commercial world, have been since the mid 90s.
i watched the indie game movie over xmas, it might have something to do with my sorting my act out a bit again too!
how much of an outlay is there for xbox dev?
i'm going the 'opengl es' route as its used on all mobile platforms cross android and apple (iphone/ipad) and is a subset of full gl on windows, and will also run on the newly announced "steam box". i'm using (free) mali sdk and emulator on windows to develop, so i've not built for any actual native hardware yet (not really intending to in the short term)
i did some native direct draw stuff in the past, but the microsoft stuff always seems to change a lot, with gl at least i'm confident it won't as i can still use (and buy for reference if i'm careful) books that are 10+ years old!