I've been a Steam member since Oct 11, 2003... I was one of the fortunate ones who had no issues with it with HL2/CS:S/etc and I never understood the complaining about it.
I <3 Steam and wish all PC games were on it
I've also been using steam since 2003. I think a lot of CS related problems were with Punkbuster rather than steam itself. At first the best thing they brought in with Steam is being able to join servers that your friends were playing on, and messaging while in game.