Laptop or desktop? Apple's laptops aren't that expensive anymore, especially if you can get an education discount. I've got the 15" MBP for work, and am going to be ordering a 13" MBP for home. $1399 for 4GB, 2.53Ghz Core 2 Duo, and 250GB HD. Compare that to a Dell XPS Studio 13 @$1100 for the same spec, and I'd personally go with the Mac because you can easily run all three major OSes on it.
Desktops are a bitch with Apple, because you've got the iMac which is basically a 24" laptop with a desktop hard drive, or the Mac Pro which is a workstation, and costs like it. There is no $1200 Core i7 machine like there is with everyone else. The Mini is cool, but is effectively a MacBook with no screen or keyboard/mouse.