Love, Love, Love my ipod touch. It is invaluable to me. The nursing apps are fantastic, complete drug guides, Taber's med dictionary and more all in one tiny device. Most of them don't even need wifi. It is a constant in my pocket at clinicals.
If I had an iphone I would just get the apps on there. I don't think they're really that big, I only have an 8g touch and it's about half filled. But I'm not that techno savvy so I don't know about the phones.
I would still get the ipod touch rather than pda. I think you can still buy ones in the stores that don't have the camera, although you may have to go to ebay etc. I think it is 3rd generation without the camera.
I will also say that it's been a bit awkward that both of my clinical instructors so far wanted to be texted when they were needed, so I ended up having to carry my phone anyway, but I still prefer having two separate devices. And I anticipate clinical sites where phones are not allowed, but my touch should be.