I've supported Steam earlier, but I'm certainly in agreement with two points here.
1) Steamworks - it's forcing a monopoly, and that's always a bad thing.
2) If I buy a game from a real store, or by post from Amazon or the like, I expect the game to be on the disc. Especially in a potential future world where the UK government is going to decide if you're guilty of piracy by how much bandwidth you use, and not need any proof to condemn you as a criminal, when I buy a game on DVD, I don't expect to have to download 15gb of stuff when it should be on the discs. Updates, patches, great, all part of the fine Steam service, but not the whole damn game. come on Steam, it'll save you money too!
Fully agree with tehroc above, too, I've probably bought at least a dozen games I've not played or only loaded up once, hell there's stuff on my list I've not so much as downloaded, purely cos it was like 'ooh £1.75? I'll probably get around to playing that sometime and it's only 2 clicks to buy it. What the hell *click*'