Should I use a mac mini as my primary desktop?

Answer 1

You have to consider what you may need in the future. As it is configured by Apple, the Mini is limited in a few ways:
Max 160GB internal drive.
Max 1.83 GHz processor.
Max 64MB video memory (probably will not handle Windows Vista's best video mode; will not run a 30" Apple Cinema HD Display).
No Firewire 800 port.

If none of these limitations bother you, go for it.