What I can say, however, is that one of the people behind the project is a Mac fanatic.
Which is funny because it isn't Mac compatible yet, however they are working on it.
I can't say much about Gametap either, as I have also signed an NDA with them, but I can say that the 5 gbs of data will get downloaded to your harddrive. It includes roms you will need for all the emulators so you don't have to download a game per play. It will automatically updates new games to your hard drive when you sign off each time.
I was going to give it a run on my system this week but since it isn't mac compatible right now, I need to install it on my boyfriends computer... which I will hopefully do in the next few days.