At Haas, 80% use a Windows Laptop and 20% uses Mac. There's no specific support for Mac but the Mac users got together and formed their own support group.
I would recommend a PC unless you've been using a Mac for a while, since you'll need to run an emulator ("Boot Camp") to run some Windows programs on the MAC. Out of all the laptops, people are most happy with Lenovo Thinkpads (I'm using one and loving it) because of their sturdiness and reliability. There are a lot of Dell users too, but many have been complaining about the quality and service and are switching to Lenovo this semester.
One big thing about Thinkpads is if you can find a IBM or Lenovo employee, you can get up to 35% off the list price, making it as cheap as any Dell out there.
Other options include Netbooks if you're not going to type too much on this laptop (i.e. you have a home desktop PC). Netbooks have a good amount of power for their size, last forever on their batteries, and is great to carry around. The only problems are the keyboard and screen sizes. If you're ok with that, then a Netbook may be good for you.
Here's a long discussion about laptops and different brands in the Knowledge Vault. I highly recommend reading through it.
108-t43003Good luck!
Kry