I've used it on my Windows partition to play a few Source mods. I also activated my Humble Indie Bundle 2 on it. I've started to get a little excited about Desura for two reasons.
First, they have stated their intention to produce a Linux client from the beginning.
Second, the games selection. There is only a handful of indie games on their client so far, but pretty much all of them have Linux clients. It's a solid enough catalog to allow a lot of us to forgo installing a Windows partition. No big AAA titles so far, but it would be a damn good start.