I got a GameTap account today (happy 4th, btw, for all you Americans!). I got it mostly to play Sega Saturn games, which are just now being put on GameTap. So far, the two games I've downloaded and played are Crazy Taxi (for Dreamcast) and Bug! (for Saturn). I think I'll use GameTap to try different games. And then, if I like them, buy them (barring games I can't play on my PC or actual game systems - which I'll probably just keep).
Crazy Taxi = Awesome game. One of the best last-gen games ever made. I think I may pick up the PS2 version sometime.
Bug! = One of those games that was pretty cool when it first came out (it was, after all, the first "3D platformer" if I remember correctly), but now seems kind of lame. There's nothing really interesting about it except that you can move in four directions rather than two (which is actually a problem in some instances since often you can hardly see where you're going and then you wind up falling off a ledge and to your death - Bug can't even grab onto ledges!). The main character is another one of those "mascots with attitude!" that were common in the early-mid 90's. And the music's pretty awful. It's basically just a tech showcase that's waaaaaaaaaay past its prime.