Fantastic

I love it. First of all, it's free. Also, it has pretty much any PC game I could imagine. The UI is simple. The review system works great and is a great indicator of whether I'll like a game. There are sales *all the time*. And, once I buy a game, it's mine - no keys to deal with, I can play it years later, on whatever system I want.

I wish every type of consumable media (books, movies, music) had something like Steam.