I really do object to the *requirement* to be connected in order to play the single player game. I may be connected most of the time through broadband anyway, making this a moot argument in terms of real effects, but I refuse, from a standpoint of principle, to buy the game until I am not required to do this. I don't particularly care if it validates me every time I start up and am connected to the net, and I dont care if it does it when I play multiplayer, but I refuse to have the requirement to be online dictated to me by the developers for the single player game.
I also strenuously object to a system that doesn't put the control of downloading in my hands, no matter how intelligent it is. I want to ensure my ability to run steam online purely as a way of verifying the legality of my copy, as well as controlling where it downloads to, and be able to back it up in a non-proprietary format, as well as having complete control over what it downloads as well as where, when and how fast. I seriously dont want to see large cache files that dont relate to anything I know about, and I also want complete control over what feedback the program gives to Valve about me, other than (as noted before) the legality of my copy.
Steam has a crappy user interface lacking in feedback, and a shocking lack of options for the user. Even Windows update isnt this insidiously suspect.