eh, i played around with it for a bit. ported a good bit of that old sonic dash engine to it, but didn't feel like writing up editor programs for stuff like maps and animation (this was before i obtained REALbasic, which is pretty good at that sort of thing). anyways, if you've ever used game maker you should have almost no problem picking it up. my gripe is that the xna framework provides pretty much only high-level access to stuff hardware functions (understandable, since its pretty much a consumer's xbox 360 sdk), which can actually be good for new programmers. also the obvious lack of portability to other OSes.
anyways, give it a download and play around with it.