Rachel, may I suggest you read this article on Anandtech:
http://www.anandtech.com/mac/showdoc.aspx?i=2232
It might give you an idea or two 😉
Also read some of the comments, I especially like the comment of this one support tech who wrote that people whine for 3 weeks after they switch from a PC to a Mac, after that you have to pry the Mac from their hands…
There’s also a interesting thread on Whitespace
http://9rules.com/whitespace/our_thoughts/mac_designers_config.php
who only recently switched to a Mac.
I concur with most of what’s been said by oyher posters. I’d just like to add if you’re buying a Mini spring for at least 512mb of RAM, 256 just won’t cut it.