I also have a tablet PC (actually, a convertible, screen-flippy type), which I use mainly to do homework. Even though I have Maple installed on the very same PC, I prefer to work out analytical solutions by hand. One can't learn any time-saving tricks if one always let's Maple do everything with CAS...
My favorite things about using a tablet are:
1. It's very quick to erase, copy, paste, slide formulas over to add minus signs, add extra space on the page if I screw up and realize that I forgot a step, etc. It's like paper, but with superpowers.
2. OneNote 2007 has drawing tools like other MS Office programs, and a wide variety of available pen colors, which means I can make clean-looking diagrams very quickly.
3. Every bit of my homework is stored and easily referenced; I print off a hard copy to turn in, but I always have my soft copy available to read, no matter how long the prof takes to grade the homeworks. It makes it much easier to study for a test, if HWs haven't been handed back yet...and if something gets lost, I can easily print it again!
4. Way, way more volume than any paper notebook! A whole bookcase-full of notebooks, all on a 4-lb. laptop with a 12'' screen.
5. Unlike paper, backlit LCD screen is easy to see in darker environments.However, these are the things I don't like about using a tablet PC:
1. It generates way more heat than paper. It gets too hot to hand-hold, so one still needs a desk, table, or other support.
2. OneNote uses a lot of memory, and the occasional background tasks can sometimes make it crawl. Can be very annoying if I just got some inspiration and was frantically trying to see whether the algebra worked out...
3. Unlike paper, backlit LCD screen is nigh-impossible to see in bright sunlight. :\When I am not using my tablet PC, I prefer good, old-fashioned paper and pencil. Not pen. I was taught never to do mathematics with a pen, because one might have to erase, and to this day I still cringe if I have to use a pen to write any formula...