Chalk another up for the iPhone 3G.
Love it to bits, I use most features everyday and rely on my calendar, which is sync'd to my iCal at home.
It's great for carrying your portfolio of images, illustrations etc. My favourit music and podcasts are loaded on to it as well.
I also have the Photocalc app, which is a great photography aid DOF calculator, sunrise times etc.
Probably won't get rid of it when my contract runs out in February, unless a new iPhone is released.