I am on my second PDA. I got my first one as a student. It was a dell, the second is an HP iPAC. I love it. I have bought a drug guide, an IV drug guide, and a lab manual, plus
skyscape throws in a free calculator called Archimedes.
It fits easily in a pocket, and I like having the drug info easily at hand, plus I use the calendar like no one's business -- I like getting those audible reminders of upcoming events.
I recommend the HP b/c it uses a microsoft interface meaning that I can upload/download word and excel documents to it.
Some would say that PDAs are becoming dinosaurs, PDA/phones are now the rage. I like having the two as separate accessories, but that may be just me. Hope that helps!