I'm surprised nobody here is talking about the real feature of Steam that got me to accept it - even to change my buying style to buy games through steam first. That's the Steam Community.

I play TF2 on the same set of servers at fairly regular times. Over the months, I've become acquaintances with many of the skilled players who also play on the same servers. When they first started sending me friend invites, I was hesitant, but decided to try it.

It's turned out to be a blast. I can look at my friends list and see when a critical mass of skill is on the server, and know the game is really competitive. I know when my favorite medics or favorite healing targets are on, and know the game will be more teamwork oriented rather than just a bunch of randoms playing solo. Plus a lot of us have started talking via the steam im, discussing our gaming rigs, our tf2 keyboard layouts, etc.

The best part was when L4D came out. Most of my tf2 friends bought it, and we all started playing L4D together. It was a blast - the same people I enjoy playing TF2 with in an entirely different game, without having to do any elaborate planning. (Heck I don't even have email address for most of the people on my list, trying to coordinate that manually would be impossible). Being able to transition into an entirely new game with the same set of good people, rather than starting all over, weeding out the 5 year olds, the mic spammers, the racists, the homophobes... was so nice.

I've switched to buying almost all my games through steam. Steam Community has also turned into a nice form of viral advertising for indie games. I saw a friend of mine playing World of Goo. I im'd him, asking him if it was good. He raved about it, so I downloaded the demo free from Steam, played it, liked it, bought it. I started playing world of goo, and two other people IM'd me asking if it was good. One of them just played the demo but didn't like it, the other ended up buying the game too. And who knows if the cycle continued. So from one sale, you got 2 more via steam community reviews. That's incredibly effective word of mouth advertising... I don't normally go around asking people about games, or raving about games I play, but if I see someone playing a game I'm interested in, I'll drop them an IM to see if they like it too. The Steam Overlay which goes on top of all games - easily toggled off and on, makes it easy to carry on conversations while playing games.

Anyway that's my 0.02$. I'm not a huge fan of DRM, but Steam's made it worthwhile for me, and added a whole lot to my multiplayer gaming experience. Plus it's exposed me to a bunch of indie titles for cheap that I would've never tried otherwise - I got AudioSurf for 2$, World of Goo, the Penny Arcade Adventures, etc, all because they were being played by friends, and had good recommendations, and were easy and convenient to purchase. :)