I actually went through most of med school and residency without a palm. i did buy one for 1st year med school, and had the whole portable keyboard thingy and took notes... but it ended up not really making much of a difference....
throughout rotations i never used it, and in residency as well. I carried around in residency the pocket phamracopeia (drugs), tarascon books (depending ont he rotation, but the Adult ER, the Pedi ER, Medicine/Critical Care), the Sanford. Got me through what I needed to.
I do little book vs. Palm challenges with med students when they show up with their fancy stuff. We'll pick a random drug name, I'll be able to find it and get you the dose before they do.
That being said, not having a PDA meant I really needed to know my drug side effects/interactions, etc, because the pharmacopeia didn't have it.
So, its not necessary if you didn't use one in the past. But if you have money to blow and like that sort of thing, its not a bad idea.
Q