I am only posting as a reaction to the poster above me really, but personally speaking, i have never had any problems with steam, and have been using it since Half Life 2 came out (which required it). Customer service does take some time, so the first port of call is always the steam forums for me. If the game is popular enough the user forums will be a buzz of activity. Whilst my list of "big" games, like Doom 3, Left 4 Dead etc, that take up GBs of space are very few, the smaller "indie" games usually stay on my hard disk drive for good when downloaded. I would be very happy if a steam purchase option was available!
Also: When you play a game on steam, your steam freinds also see that you are playing the game. What better marketing ploy than to know you have freinds playing a game you've not heard of!