I used to be an iPod/phone/hipsterPDA/pen/keys/wallet kind of guy. It worked, and subsequently it changed my pants buying habits for a while. I was later provided with an iPhone and ever since I have been an iPhone/keys/wallet kind of guy.
I suppose the answer is that I prefer separate components if they do the job better than a single device. I have been happy with the iPhone as a substitute. Years back I had a Palm Zire and it just didn’t cut it.
I still keep a Moleskine handy, just not in my pocket.