Well I had a chance to use an iPhone for a longer time and discovered few things in regard. First of all I would like to use PM or a similar app with it since it is a great tool for viewing photos (maybe better for that than being used as a phone). And it really misses a good image viewer since its built in one is way to basic for my taste. No options to search, to sort or to filter. These options from PM would be really great to have in a pocket.
I cannot really imagine how editing, IPTC-ing or anything other than just viewing could be done on iPhone. It lacks the keyboard which (together with the many shortcuts) make PM that fast and effective. The keyboard it has I find hard to use for longer time, and the device also lacks text copy+paste functions as well as file management the traditional way. It can only handle images synchronized from iTunes (that uses iPhoto or Aperture libraries), and as most important in a PM context the iPhone lacks any direct connection possibilites to images taken. You need a computer to put images onto it.
So I think iPhone is not the perfect device for using it for work (image editing, selecting, sending), more like a fancy gadget you can play with and it may be used to show your last shootings, portfolio, etc. On this end a somewhat simplified and view only oriented - just show images and allow for search and filter the way PM does - app would be nice (I would greet one such for desktop to acompany PM as well).
However a PDA app could be useful for field photogs to quickly select caption and send, maybe keyword, color code on the go.
