I was chatting with a friend over lunch when the topic of game gifts and Steam came up. One of my favorite things about Steam is the ability to gift a game to someone else. There is something pleasantly personal about choosing a particular game that a particular acquaintance may enjoy. Even more worthy of praise is Steam's support for owning extra copies of a game. That is, if I own a game, such as Half-Life 2, and then buy Orange Box which contains Half-Life 2, I am automatically credited with another "copy" of the game that I can send to a friend. How awesome is that?
Using Live, it's true that I can buy someone points to similar effect, but it not only lacks that personal touch, but is oddly impossible to do via the 360 interface, where I normally buy points. Weak by my reckoning, at least.