several years back, someone I knew was a resident in a hospital that required everyone to have the same PDA in order to have near instantaneous information sharing (i guess, on patients with urgent medical problems)...
Right before she went into residency, though, she had bought an expensive PDA that she ended up NOT being able to use at all b/c her PDA was not compatible with the one the residents were supposed to be using (BAD EXPERIENCE for her since she couldn't return the PDA she'd already bought and was on a tight budget). this was some years back, so I'm not sure if those kinds of problems could still happen today with all the patches & software available (and also, I wasn't that interested in PDAs at the time so I didn't bother to figure out exactly what was the problem), but still,
i would check with the other students at your program (med school? residency?) for advice first. They might have helpful advice for you in making a longterm investment.