It's a fantastic bargain, just bloody annoying that there's no discount if you already own some of the games. As far as I recall you can't even gift the ones you already have.
edit: Chet, don't bother with SR2 - the engine is massively buggy, suffers from terrible frame rate problems when you travel at any decent speed in a car/bike which makes it almost unplayable. Plus, if you must get it it's probably really cheap retail, and the retail version links to steam anyway.
You can back up the game content from Steam, and they've said that they'll probably release updates to the games to allow them to run independent of Steam should it go tits up. They probably will should that happen, but it's an if and so paranoia about it is entirely justified.
Good points on the steam tits up, i dunno, maybe i'm a bit too old school and like the boxes. Usually go for the collectors edition on all games, just because of shiny thingies *hugs his pipboy bobblehead*