I think where Steam is great is for indie games, the indie bundles in the same were by and large fantastic and ive really been impressed with stuff like Edge and the bit trip games, id never pay £6.99 for them on their own but £6.99 where you get 6 or 7 games, finding one or two out of that you will play is great way to sample things.
I have over 200 games on steam now, Ive got about 50 that I keep on my hard drive, the other 150 id never play, i would love it if steam would give you an option to recycle games or donate them for a small donation to charity or whatever to keep your steam folder a bit more manageable.