I've had an iPhone 3G for four weeks now, so I'll share my own impressions, both good AND bad. Hopefully, this will be helpful.
The good:
- Phone reception and call quality are as good or better than any other phone I've owned. People have told me that I sound much clearer than I used to on my previous phone, a Nokia 6682, or on my land line. Signal strength is comparable to Nokia. If the 3G signal gets weak, the phone switches to EDGE without a hiccup -- no dropped calls in my experience. The 3G coverage seems pretty good in the Triangle -- I seldom see the phone fall back on EDGE.
- All the phone features are easy to use. I love the ability to listen to my voicemail selectively -- you access it through a visual inbox, like an email client.
- PIM and email features work well. I use Gmail and Google Calendar, and Plaxo as my address book, so I could just use the excellent built-in browser. However, the client features are implemented so well that I've set up the phone to synch with my online accounts. Push email works perfectly, as does the calendar. Push email works with Exchange Server, Yahoo Mail, and MobileMe. Exchange and MobileMe also support push contacts and calendar. You can set the phone to fetch from Gmail or any other IMAP server every 15 minutes (or less frequently). This works perfectly, too.
- Internet connectivity and browsing experience is amazing. I do almost all of my personal "computing" online these days, so I wanted a phone with a good browser. The iPhone has more than exceeded my expectations in this regard. The browser is a REAL browser, not a WAP browser, so pages render as they would on a computer. The pinch and tilt features work better than advertised. The phone switches between 3G, Edge, and WiFi automatically and seamlessly, always choosing the fastest option. 3G connection speed is better than I expected.
- I actually like the on-screen keyboard. Since it's Querty, I find that I type text faster than I used to on a typical phone. The autocorrect feature is very smart and seamless, although kids might be frustrated when it corrects their
l33t. I do realize that some people may miss the tactile aspect. I don't.
- The killer feature that leaves all other phones in the dust is the app store. I've found that I use my phone as a computer more than I use an actual computer. I could not have imagined that before I got the iPhone. Granted, a lot of the software in the app store is utter crap, but there are some seriously jaw-dropping exceptions. I'm not going to list every app that blew my mind, but I have to mention
Dynolicious. (Anyone want to turn a local parking lot into a skidpad?)
- The SMS client implementation is slick. It has the look and feel of an instant messenger (iChat, specifically). For me, this is one of those pleasant surprises that changed how I use my phone. I used to text very sparingly, and given AT&T's unreasonably high (IMO) price for the SMS package, I wanted to get away from it. Instead, I've gone the other way -- I use it more often than I make phone calls -- it's just so efficient and easy.
The bad:
- The really disappointing and frustrating thing so far has been the "crashiness" of 3rd party apps. Seems like once you install a lot of them (>20, let's say), you start to experience random crashes. I've actually experienced a couple of occasions where ALL of the 3rd party apps would crash upon startup. What seems to have resolved the issue for me was deleting all the apps and reinstalling them on the phone directly from the app store, bypassing iTunes (you can reinstall paid apps for free). What a PITA!

While there may be some less than stable apps out there, by all accounts the fundamental problem is Apple's. Supposedly, the firmware upgrade that's coming out today will fix this, but we'll see...
- No cut-and-paste. I personally have not found this to be too much of an issue, but it is a common complaint on the internets.
- No MMS (multimedia messaging). Again, a common complaint that I have not had much of an issue with. The integration of email into the photo browser and other apps is so seamless that I've forgotten that I used to use MMS a lot on my previous phone.
- Relatively weak camera for this day and age: 2 megapixels and no video recording. My Nokia took terrible photos and unwatchable blurry video, so this is somewhat of a step up for me, though. I've used the camera a lot more than I expected to, but it would be nice to have better specs.
- Another non-issue for me that seems to bother others: You have to use iTunes to synch your music/video and install firmware updates. (I'm probably the only person out there who actually likes iTunes, but that may be because I don't use the bloated Windows version.)
- The iPhone is delicate. You must get a protective sleeve or case for it, and I would also recommend a screen protector.
Overall, the iPhone has exceeded my expectations. Until recently, I considered the iPhone to be a useless expensive toy and was planning to get a Blackberry Pearl. When Apple added 3rd party app support and dropped the price to $200, I decided to take a chance. It has been a pleasant surprise. Your mileage may vary.