orcishgamer: Check the specific sub forums for the game you want for common problems. Some work out of the box, some have minor problems (e.g. you have to set processor affinity or some such), some seem unresolvably broken for some people. In general they're pretty functional for the great majority of players. But these games are old and OSes have changed. Hell, I remember games I'd purchased not working out of the box very well and never getting any patches, back when many of these were released. It's PC gaming, it's just kind of what I expect.
What he ^ said. Most games work fine for most people. Some games requires some tweaking for some people. Sometimes, those tweaks that work for one game will solve the problems for many other games (run as Administrator, for example). Odds are, if you have a problem you won't be the only one, and that's where the subforums come into play.
If you don't have tolerance for a (low-probability) crapshoot when you buy a title, this might not be the service for you since there are no returns - once you bought it, you bought it, warts and all. This might be true of the other services, too.
