I've used PDA's for taking lecture notes and at uni for 3 years. First, I had a clie Nr70v, then an NX80v, then UX50 (Briefly) before getting a Zaurus C860.
The keyboard on the Z is incredible compared to those of the clie's. The only problem is the fairly loud clicking noise the keys make, in quieter lectures, you may feel like you are disrupting things a bit! But typing is so much faster than writing on paper, and you can easily upload the notes to your main computer. Well worthi it!
Also, if your uni lets you, you can download the lecture slides and have them on your PDA too.
With the NX80v, I'd just take photos of the slides with graphics (The camera was good enough, unlike on the NR70 or UX50).
I did do some diagrams on the Nr70, but I would recomend taking a note pad + pen for diagrams. I know it's nice just to carry in a PDA in your pocket and nothing else, but for diagrams, I don't think a PDA is near as good as a pen & paper (Unless it's got a decent camera). If you can do the diagrams quickly & accurate enough on the Z, then great, but you may find it more hastle than using pen & paper!
Overall, i'd say the Z is a great investment for uni;
- You can take journal articles etc in PDF format to read when you've got spare time
- You can take lecture notes and easily upload them to your main computer
- The keyboard and screen are good enough that you can go to the library and comfortably write up an essay
- You can listen to music while doing your essay & traveling between home & Uni (If you want!)
- If you get a little condenser mic, you can record your lectures as Audio (I did this sometimes, but never actually listened to them again!)
- You can play games in boring lectures
- Great organiser
All in all, a great help to uni life! I recon the Z is the best out there for Uni, due to the great keyboard and screen combo, & OK software.