At the moment I use my A500 for basic retro gaming (Lemmings, Marble Madness, Zany Golf, that sort of thing) while I wait patiently for projects like Clone-A and OS4 to come into full commercial production :-).
As for my reason for sticking with Amiga, well, I can't really say for sure. There's just always been something about an Amiga that I can't seem to find in any other system :-)
(Edit: excluding MorphOS of course since I haven't actually tried it yet and as such can't really say how "Amiga" like it is)