Over the years, my friends & I have held our own little closed circle lans. Steam sucks in terms of these lans. The protections it imposes kill off the potential of buying one copy of a game to play with friends at a lan, and the chances of me & my friends actually all having purchased the same game is pretty slim. So yeah, at our lans we typically end up playing older games (warcraft3, jedi knight II, etc) simply because none of us are going to shell out ~50$ each to get "that nifty game we'll play once before we decide its boring" and because older games often were setup just so you actually could buy one copy and host a lan with it, at least just to get your friends interested in playing it.
Aside from that, about the only thing steam does right for me is exposure to games. I've purchased numerous games just because steam happened to mentioned they were on sale and I had never quote gotten around to buying them yet. Aside from L4D, I've only used steam to get single-player games. I do like how they have rereleased some old classics (like xcom) in nicely maintained packages that install without concern even on new systems.