This thread is a little old, but I thought I would throw my 2 cents out there. I'm an astrophysics major and purchased a tablet last semester. I purchased a Fujitsu Lifebook T2010 with an extra gig of RAM. It came with Vista business and is not a powerful computer, but works wonderfully for school. Reading most of the replies in this thread, I don't think many people actually understand the benefits of a tablet over paper notes or a laptop.
First, as mentioned, you may be able to type faster than you can write, but typing equations is difficult and not always easy to understand. Tablets are great for writing equations. The bad handwriting thing is true to an extent. If you have bad handwriting, you will still have bad handwriting when writing on a tablet. Often the text conversion does not guess your words right and you have to correct it. That is IF you use the text conversion. I have yet to use it so it really doesn't matter as long as you can read your own handwriting.
I think the best part about having a Tablet is the ability to keep everything organized. You can quickly highlight your notes to add a color dimension in there. This is great for key terms and stuff you know will be on an exam. If your professor missed a part in his lecture and goes back to add something, you can simply create space in your notes by moving all of your writing down like you would when typing a paper. You can put notes into separate folders and notebooks organized however you want. You can also keep old notes without keeping huge binders. This comes especially useful in series classes like calc. If you want to print off these notes so you can have them for reference without having to turn on your tablet, they take minimal ink. I printed on my Dell printer on the lowest possible setting (150 dpi) and they came out smoothly.
Reading is terrific with a tablet as well. If you have the time to scan all of your books, or if you can find ebooks, you can read all of them from your tablet. Definitely a lot better than having to carry them with you. When you have the tablet in tablet mode it is about as big as a closed book too, which makes reading on the bus or in a coffee shop much easier since you don't take up much space. I know there is software that lets you make marks on pdf files so you can highlight and take notes as you read, but I have not bothered to look yet.
If you do decide that a tablet is for you, I have a few suggestions. You want something that will have a good battery life. Most tablets are made to run long periods solely on battery power. Mine typically gets 4-5 hours which is perfect for getting me through my classes. Also, you want an active digitizer. This will give you the best quality of notes with no accidental blobs showing up.
Tablet PC Reviews has good reviews of most of the major tablets on the market. I would definitely suggest checking there for a good tablet and I would avoid HP. I picked up my Fujitsu on newegg for $1500 which was a good deal as I get more use out of it than I ever did my Dell I bought two years ago for $2400.