i use now an iMac and LOVE it. Word on the street is that Apple has lots of issues with the latest models but I was lucky and got a very good machine.
As far as using Blender 2.5x goes, there are no problems and all the menus display like they do on the Linux machine.
3 years ago I bought an HP Media Center, upgraded it with a better power supply and an Nvidia GT7600 (instead of some internal on-board-chip) and a slim super fast version of XP (with all the junk removed). The AMD X2 5000+ with 3 GIG of RAM renders the blender benchmark scene around 1:20 seconds. Under Linux the render time was around one minute to 1:25 depending on the distro.
The new iMac renders the blender benchmark in only 11 seconds (with blender 2.50) and comes with 4 GIG of RAM out of the box. Rumor has it that Apple “downgraded” the performance of the ATI card because of excessive heat issues but I can load huge blender scenes and have to troubles rotating the stage without delay.
The 27 inch screen is very nice to work with.
If you are going to get one, do yourself a favor and buy the extended warranty plan!
Also, you can buy from Apple direct via your college … I did and got a nice little discount and the warranty was cheaper too.
The Apple forums are buzzin with all kinds of love/hate stories so it pays to read up a little more.
For what it’s worth, I am happy to say that this is the best computer I have ever owned! Even gave it a little spot on my new home page