Yes, totally agree on the games front. The Mac Mini wasn't built to play the newest games. The graphics card only has 32MB of RAM for goodness sake! The games bundled with it really are dire as well.
If, on the other hand, you want a first class operating system - OS X is one of the best around - on a par with or better in some areas then XP, then get a Mac Mini. If you want to do basic productivity tasks like surf the Internet then get the Mini. If you want to use the iLife suite of programs (iDVD, iMovie etc.) to edit your DVD's or Movies' or to create music then get a Mac Mini. And if you want a securer system then XP with fewer viruses, no spyware and better security then get a Mac Mini.
If, on the other hand, you want to play games then, sadly, steer well clear.
I have both a PC and Mac Mini sharing the same keyboard, mouse and monitor. I have to say I use the PC more then I do the Mini by quite some margin. Probably because all my games are on the PC and I'm used to the operating system.
There's nothing wrong with the Mini. It boots in half the time my PC does. It also runs extremely silent. It's just that browsing the Internet is a wee bit sluggish and some programs I just can't find equivalents for on the Mac. On the other hand, the Mac operating system is so simple to use, no tweaking the registry or messing about with msconfig and services to optimise your PC.
Considering that the Mac was half the price of my PC when new and that it's about a tenth of the size of my PC, I'd say it does a damn good job of any task that's set it. It is a little bit sluggish but the processor is about half the speed of my PC's (in terms of Ghz) and the performance difference is nowhere near that. I'd say it feels more like a 2.0GHz machine. Now, what I'd love is a PowerMac G5 - maybe in my dreams