To those worried about having "some additional software" just for one game:
Years ago I had to get STEAM in order to get the MOD (which later became a full game) called "Red Orchestra". I thought it sucked that I needed STEAM and never thought I'd use it for anything else. Then I started paying attention to those unbelievable sales seemingly always going at STEAM (nothing out there beats them.......I mean NOTHING) and I now have 200+ games on STEAM.
To those worried about "losing access to THEIR purchases":
Even in situations where people have been caught cheating in games (ban-worthy offenses) I have never heard of people losing access to their entire library, just that one product. What's the problem there? Simple.......don't cheat. If you do, you deserve to lose access to the software being used regardless of the fact that you "paid for it". Oh and I do know about that MW2 fiasco where VALVE banned a hell of a lot of people erroneously..........again.......erroneously......and everything was set straight.
I have in my many years of being a STEAM customer not had one single issue. I run STEAM on 7 different machines, sometimes in OFFLINE sometimes in ONLINE, sometimes in PRIVATE and sometimes in PUBLIC modes. I have at various times in those years downloaded and re-downloaded many of the 200+ titles in my library all without one single hitch. Steamworks makes finding/joining/inviting to games the easiest thing on the planet. If you don't want your stats visible for everyone make your profile private. There is simply nothing else quite as simple as STEAMWORKS in existence.
For many years STEAM was the ONLY non-windows/OS piece of software besides TeamSpeak on any of my gaming computers. Then with the advent of Impulse and EA's new Origin I had to add a few pieces of software to the stables. I can tell you that everything I just said about STEAM I cannot say about the others.
Since the following comment seems to have stuck a nerve and I agree that my use of the term "assumptions" below of course in itself implies an assumption on my part. So if you're not one who silently "assumes" STEAM doesn't work for anyone disregard the below. Thanks!
So while I'm sure there are those who's experience with STEAM does not reflect mine, please cease with the assumptions that experiences such as mine do not or cannot exist.