I haven't looked at tablet pc's in a while, but you pay more for what you get from what I remember. The bang-for-buck wasn't there. The processors were slower, the screens could be smaller, and you paid more for them than you would a laptop. The company I work for makes medical software that can run on tablet pc's, btw. I played around with one, but wasn't overly impressed.
I'm with DaGlyde and Vengenance on this one...IBM Thinkpads are more robust then the Dell Laptops, and I've head that Sony Vaios are pretty good as well. If you're worried about cost, if possible (and you may know this already) buy your computer through your school. We bought our IBM T42 through UCSD (University of California, San Diego) and paid about $2000 for it's Marketed Price $3000. My buddy who recently got into Graduate School in UCLA just did the same thing. Actually this morning, he bought a $2100 IBM Laptop that's listed at about $3000.
Yea, it was kinda fishy when they raised the prices of the laptops, only to give out those coupons thereafter. Just pay attention to prices on www.techbargains.com, and you should come out with a sweet laptop. I wanted to buy a Dell 700M for $750, but they raised the prices. Waiting game begins until they drop the price again. It should be a week or two.