1) The games should ask you to configure the controls on the very first run. I keep forgetting to configure them, and then I have to back out and do it and then run the game again. Obviously this doesn't apply to modern PC games that have internal configuration menus.
2) Gametap TV sometimes doesn't load videos at all. Strangely, it has no trouble loading the ads before the videos. :-\
Edit: Since upgrading to Gold, the problem videos from before seem to be working. Maybe they weren't supposed to be usable from the Free account, or maybe Gold users get priority on the streaming lines.
3) We should be given some advanced video or audio configuration options for emulated games. Maybe keep them hidden from casual users or something. I'd like the option to use 2xsai and cubic filtering on the audio, at the very least.
4) Some of the emulated games have very minor static in the audio that isn't in those same games when I play them on my own emulators. Audio emulation can be quite poor on some of the older titles in general. Joust, for example, sounds pretty terrible.
5) If you need your Nintendo brand fix, you're out of luck here, except for the Konami pack, which has the Castelvanias and Contra from NES emulated.
6) While downloading games in the background, Gametap performance overall is hurt. For example, while I'm downloading 4.8GB Tomb Raider Legend right now, all my games are suffering noticeable stutters, as does the Gametap menu.
7) I tried Chu Chu Rocket for Dreamcast but no matter what I do I cant get my mapped controls to do anything in the game. The other DC games might have this problem.
I'll be adding more later if I find any. Overall, this is a fantastic service, especially for retrogamers with busy lives who can't deal with the complicated aspects of normal emulation routines, not to mention the legal issues.
I'd also like to point out that, as a video editor, I admire their efforts with their ads. They can make even the oldest, or most obscure, or just plain shittiest game ever, appear worth playing. Sometimes they even craft up an ad/trailer for a game that always had terrible videos to show it off.
Looks like I've found two massive issues
http://www.gametap.com/forums/thread.jspa?threadID=2894 *Fixed. nForce Networking Configuration Tweak required.
http://www.gametap.com/forums/thread.jspa?threadID=2916