I use a Mac, and would never go back to a Windows PC now. From my experience they just work better (unless you know the ins and outs of building PCs), Mac OS is fantastic to use and they just look great. People claim they're overpriced but honestly, those people have probably never used one. When it comes to quality, you get what you pay for.
Also, think hard about wether or not you want an iMac or a MacBook Pro (about the same price). I bought an iMac because I wanted a bigger screen, but sometimes I wish I'd done what my friend did and bought a MBP, then hooked it up to a larger monitor. Having a laptop you can take with you to portfolio crits, interviews and placements is a big benefit.