I have a Mac Mini, and I love it, seriously it's one of the best purchases I have made along with my iPod Video,.
I use both Final Cut Pro and World of Warcraft, the Mac Mini runs both fairly well to my surprise but be warned it still can't keep up with the G5 iMac.
World of Warcraft does run a treat, the graphics are pretty smooth and I find it's less laggy compared to my other Windows machine (yes I do know XP IS COMPLETE TRASH).
Overall if you're going for a good cheap multimedia computer that can do music, video and some games go for the Mac Min it wont dissapoint but if you are into serious games you can't go past the G5 iMac.