A client bought me an iPhone for Christmas (more-financially-successful friend's instant reaction: "You aren't charging them enough.").
My reaction is that while it's an incredible gadget, it's a pale shadow of the Kindle when it comes to reading. I am dismayed by the number of people who say "Well, the iPhone ought to be the ultimate eBook reader." The screen resolution is a joke compared to the Kindle. I was reading MSNBC on the iPhone a few minutes, started up my laptop, and thought "Oh man, this is much easier to read." The Kindle screen is that much better than my laptop display than my laptop display is to the iPhone.
Sadly, though, the browser that comes in the Kindle is very poor and I can't help but wonder if Amazon isn't content to keep it that way (Web browsing on the Kindle is via Sprint, fully subsidized by Amazon).
Having the Kindle for 6 weeks has made me realize how little I read mainstream books -- I read technical books (so far, none available in "native" Kindle format, although I've had luck converting PDFs from the Pragmatic Bookshelf) and a wide variety of magazines, none available on the Kindle. The lack of magazines is especially frustrating for me, since magazines come to Hawaii via boat and I receive them all a month or more after their cover data (and, of course, most subscribers receive their issues well before the cover date).
Another iPhone reaction relates to its locked-in development. For the moment, the only way to write a 3rd-party app for the iPhone is to develop an iPhone-friendly Web page; there are a few proprietary extensions, but mostly it's CSS and JavaScript. I have to say that there's a certain "constraints are liberating" aspect to this: the vast majority of PDA programs (todo lists and so forth) are easily-enough ported to the Web.
Newsgator's iPhone interface is excellent.
It seems that the iPhone only syncs email and calendars with Outlook, which is a disappointment, since my Outlook install seems to have been poisoned (it only runs in /safe mode no matter how many times I run scanpst) and I have been seriously considering switching to Thunderbird.