I use mine all the time. It keep my appointments, addresses, notes, and basicly everything. A program called documents to go allows me to read and modify MS Word and Excel documents. It is really cool. The Sony has a built in MP3 player and uses memory sticks. I have an 8 MB and an 128 MB sticks. I can carry tons of crap on it.

Check out the Treo from Handspring. Should be really cool when it comes out.