It's true that the same account will only work on one computer at a time. But I'm almost sure we've played different shared games on different computers at the same time. I know you can't play the same game at the same time on shared accounts, though. If you try it, it gives whoever is not the owner 5 minutes to either buy the game again or quit playing. I'll test it out later when I get a chance to verify whether you can play different games at the same time, though.
But even if you can't, there are still benefits. For one, having the games shared on separate accounts separates your saved game files. That's a big bonus right there. Some games, like Skyrim, won't support that, though. With Skyrim, you can only have one game going, no matter how many profiles you have.