(Prepare yourself for my wall-of-text entry to this thread.)
I use Steam on a regular basis.
The possibility of it going down at some point or me being banned for an unfair reason I view as an acceptably small risk, and I weigh this up against the benefit of being able to very easily buy games, download them and install them as well as the fact I can get games cheaper than what many retailers in my country typically ask, if they are even allowed to be sold in this country at all. I also factor in the fact I won't be able to resell games when I decide the prices I'm willing to pay.
Those who choose not to buy games
because of Steam, I'm sorry but there is no simpler way to say it than:
You will be left behind.
I've had headaches using GFWL and Starforce. These things significantly deter me from buying any game that uses them. (I haven't bought a game with Ubisoft's online DRM but I assume that'd be even worse.) Steam for me has finally managed to reach that point where I consider it to add a small net positive value to a game purchase. I'm fully aware that "buying" a game from Steam does not amount to anything more than 'attaching' that game to an account I hold with Valve. This does not bother me deeply. I pay money for games so that I can play and enjoy them, not so I can feel good about the knowledge I could play them in 20 years time even if Valve and Steam no longer exist.
Valve, with Steam, have managed to significantly streamline the process of acquiring game licenses and installing games, and to some extent managing collections of games. It didn't used to be the case, but I now consider games that require CDs or DVDs to install to be a nuisance. I can be downloading 5 games at the same time (without personally attending to the computer), and when they are finished it takes on average less than a minute or two for the first-time setup of the game before it's ready to play. Compare this with juggling several game discs and being required to babysit the install process. If I'm paying something like $5 or $10 for a game it's not unreasonable for me to expect to spend as little time as possible just installing that game. This is one of the biggest reasons I have come to appreciate Steam as a service (still far from fanyboydom though
).
It's true that these days I have a mostly reliable broadband connection and expect to at most times in the future (I don't really play games when I travel) so the fact it (Steam) can be a more negative experience for people with expensive download quotas or limited access to internet does not factor into it much for me.
Aftershafter did link to a thread where I posted about a problem I had getting Steam to run in offline mode when my internet provider was unreliable, but it's a distant memory now and I did happen to find a simple work-around at the time anyway.
I have to say I find it a tad amusing the divide that discussions about Steam can create betwen gamers. Most people who use Steam regularly find its service to be satisfactory, if not very positive. This includes me. I say this as someone who found the level of service provided by Blizzard for one of its games to be unacceptably poor. Blizzard is a company that many gamers cannot or choose not to fault.
The reason I'm pointing this out is that it's quite likely that those who come to threads like this to post about why they like Steam are doing so because they only want to help. I see some of the posters in this thread having objections against the service which I believe would not be so significant to them if they actually used the service.
I'm not interested in fighting some battle over DRM or consumer rights, and by doing so boycotting some service or refusing to accept it. As someone not from the US I'm already used to having to settle for less when it comes to levels of service. I figure one may as well go with the lesser of the evils that can be chosen from.