Ah, yeah I forgot a couple features.
You can always reinstall all your games on any new computers without any issues, and uninstall and reinstall any game you've purchased at any time.
You can also register the CD Key of a game you've purchased in a store on Steam (that's also available on Steam) and you will be able to install it on Steam as well, granting you all the features you would have if you'd bought it on Steam in the first place.
If your game wasn't available on Steam you can "add a non-steam game" to at least give you the ability to launch the game from your Steam Games menu, keeping all your shortcuts neatly organized.
Steam is simply right now the ultimate gaming service. I can only hope other companies including console companies do their best to emulate it in the future.
