As a PC tech I could make all sorts of Mac jokes...but the truth is I like macs just fine. The down side to the mac mini is cost. for the same $800 I could build a better PC for mame.(for $800 I could build a darn nice machine for anything) If you need it for it'a size then that's another thing entirely but still then there are other options for your $800.
$800? Yes, for the higher-end one with the DVD+/-RW drive. The base one is $599, and can be had for even cheaper in their refurb section...
For small form factor PCs, which is what this guy is looking for, it's tough to find a better price/power, or price/quality, ratio. I own both an older G4 Mac Mini and an older mini-ITX system, and quite frankly, the mini-ITX system is junk. It's underpowered (even for its time) and the tv-out is blurry. Worst of all, when you add the cost of the mini-ITX board, the case, the memory, the hard drive, a slim-line CD drive, and the video card (to avoid the blurry tv-out), you're pretty close to that $599 and almost twice the size.