OK, so I broke down and got one. The two of you out there who are actually surprised that I succumbed, talk to the others - everyone knows I can't resist a new toy!
Overall, I have to say I've been very impressed with the performance so far. Admittedly, I wouldn't want to try doing any power emailing on this thing, but for short notes it is actually very handy (important safety tip - do NOT use this while driving! Only very foolish people do things like this...) Everything on it functions as advertised by Apple, something I've come to expect from their products.
The third party apps I've downloaded have been very handy as well. AccuFuel is a neat little application that tracks my gas mileage for me, and I've got NetNewsWire on both the iPhone and the MacBook now, so they remain in sync with each other - no tedious rereading blog articles.
The only things I have issues with so far are the lack of an accesible file system (I'd love to be able to copy files to take with me and review at my leisure), any type of productivity suite (even a text editor would be good), and the fact that the shows I record using BeyondTV will not play back correctly on the iPhone (this is a glitch in BeyondTV - they haven't updated their H.264 codec for the iPhone or iPod Touch yet).
Otherwise, I'm loving this little toy. And the battery life is actually pretty good, if you follow Apple's advice and turn off the servicces you're not using at the time (like the GPS). They all come turned on by default, so check your system settings!