I think that the iPhone is a quantum leap ahead in personal communication compared to the competition, in many ways, but in other ways it falls short. I think that for personal use it will work well, but for corporate environments, it's not quite there yet. Many corporate environments forbid camera phones and any unauthorized camera. Anyone giving a presentation of any kind must lug around a notebook with PowerPoint on it, or at least a USB memory stick with the presentation on it to give to the one person in the room with the notebook (which is connected to the large external display). It would be nice if iPhone were more or a PDA that would run 3rd party applications like Microsoft Office... you could just plug-in iPhone through the bottom connector to the large display and give your presentation by pressing virtual buttons on its screen to advance or review slides. The ability to handle 'Office' files will help promote iPhone very far, because whether or not we like, the world runs on MS Office.
Seeing Safari run in full screen mode with ability to zoom-in to read the text and see pictures is really very nice, and the interface to do it is nice as well. The iPhone just needs a little more Newton in it make it an excellent product. Perhaps the next iteration of high-end iPod will share those features - editing contacts, calendars, and notes and syncing them with your Macintosh when connected through iTunes.
Another feature that the iPhone should have is true GPS Global Positioning integrated with Google Maps - this would be a killer feature!
There needs to be a way to make truly recordable movies with sound... There's nothing quite like talking to your family long distance, placing them on hold (or not), and taking a small movie of your toddler taking his or her first steps and sending the movie via e-mail or syncing with .Mac to your webpage. Would be pretty to have a camera on the same side of the display with granda on a video conference call telling the baby to 'come to grandma' as the toddler takes its first steps towards iPhone and recorded for posterity.