As an iPod touch owner, don't reasons 3, 5-7 apply to your iPod touch as well? Those you can do with your touch.
I feel like the most compelling reason, for me (I'm an iPod touch owner also looking to switch :) ) is the constant connectivity. I've been frustrated whenever I've wanted to look up something, or just read blogs and not having wireless available.
I also think using the iPhone address book would be great to keep track of clients and their contact information. From one screen, you can email, call, or even Google Maps them!
10 Ways Professional Photographers Can Use the iPhone