You'll find far better email clients available on WM/Palm devices, and there's more flexible and powerful calender apps available on those platforms too (and quite possibly Symbian too).
Flash doesn't work on the iPhone's Safari browser, neither does Java and I don't think it natively syncs with Thunderbird either. Last time I looked, you couldn't use the iPhone as a modem.
I could be wrong here, but I think you need to use a 3rd party app to use the iPhone as a mass storage tool - and that means running the risk of having your phone turned into a brick. I don't think it does Bluetooth file transfers either - in fact, it
doesn't do a great deal of Bluetooth, full stop.
AFAIK, if you use iPhone it'll want you to be tied very closely to iTunes too.
Incidentally, the Treo does most of the above, except no Wi-Fi, Flash browsing and USB charging (unless you use the Windows version). The Nokia ticks most of those boxes, albeit at the expense of a pretty horrible form factor/interface.
One thing: if you get a 3G/unlimited data deal, the need for wi-fi does decrease dramatically. I don't miss it and surfing on a small screen is always going to be shit if you're looking for a full graphics experience really.