Steaming along
Like Adam, I took the plunge a week or two back and installed Valve's Steam. The only Half-life game I play online regularly is Day of Defeat, but I was interested to see what Steam was about, and also interested in trying out some of the other Half-life games without having to hunt around the web looking for game-specific patches.
My experience was mixed. Steam itself seems quite slick--the unified interface is great, my games suffered none of the performance problems others have noted, and I'm a big fan of letting Steam take care of keeping the games automatically updated for me.
Nevertheless, I uninstalled Steam after about a week's worth of usage. The reason is the oft-noted (Adam comments on it as well) tendency of Steam to increase Windows boot-up time by a full 5-10 minutes. Before Steam, Windows booted up reasonably quickly and let me go about my business right away, checking email or whatnot. With Steam installed, Windows would sit there for several minutes just grinding away at the hard drive; the system activity was so high that doing anything else with the computer while Steam was loading up was impossible. What on earth is it doing? Various solutions offered by residents of the Steam forums failed to solve my problem. So I uninstalled and resolved to wait until the next version of Steam is released.
And now it looks like a new Steam release is in fact available, so I may give it another whirl. It's an interesting idea--now to iron out those glitches.