I did some sort of beta test for the company who "powers" EB1. I imagine it's pretty much the same setup. I almost finished "Dungeon Keeper 2" and started "Alice", before I lost interest.
It worked like this. You run a small program and it downloads a "cache", I opted for a full install which was 600-700mb or basically the whole game (there probably was a smaller option). Once that was done, you click on the game and it runs. Works pretty damn spiffy really.
But who wants to pay $5 for 3 days use? Most of those games can be had for $10-$20 anyway.