Before I bought my iPhone and switched to AT&T a few months back, I used a Windows Mobile 5 smartphone with Sprint as my carrier. Ever since buying the iPhone, I've noticed that some of my mobile habits have changed. In some ways it's difficult to tell if these changes are for better or worse, but like a marriage vow the commitment was made when I agree to two years of service with AT&T and spent the money to buy the iPhone.
The first thing I noticed was that I don't run around my house trying to find my iPod nano every time I go out on foot. Working from home and having everything from Starbucks to a Post Office within easy walking distance, I usually find myself running errands on foot at least once or twice a day and I usually want to listen to something as I do them. So, having my iPod and phone in one device has saved me time trying to remember where both devices are (as well as some space in my pocket).
The second thing I noticed is how regimented I've become about checking my email when I'm not home. Sprint's EVDO connection was much faster and Windows Mobile offered more frequent times for checking my email automatically. So, using my old smart phone I was always checking my email and sending replies regardless of when or where I was. I also became quite good with the BlackBerry-style keyboard and the text auto-complete feature in Windows Mobile (sorry, I really love Apple, but the iPhone has light years to go before its auto-correct is near as good as the Windows Mobile auto-complete).
I found myself checking my email less frequently on the go. I found that I became frustrated with how long the process would take (compared to my previous experience) using AT&T's EDGE and quickly got in the habit of only actively checking for new messages if I was within range of a WiFi hotspot (thankfully, there are several between me and most of the places I go on a daily basis). I do leave the auto-check feature on for the most frequent setting, every half-hour as well, but that larger interval combined with the speed of EDGE means that on average I check my mail a couple of times an hour now as opposed to probably ten or more times an hour before.
I also find that I reply to emails directly from the iPhone far less frequently and with much more brevity. This is a combination of the onscreen keyboard and the limitations of EDGE performance. I used to immediately respond to most emails on the spot. Now, I find myself putting off sending anything that involves typing more than a few words as it does take me noticeably longer to type on the iPhone. I can only manage to type accurately on the iPhone's onscreen keyboard with one finger (at least in the portrait orientation - in Safari when the keyboard is expended in landscape mode, which isn't supported in any other application, I can type pretty well with my two thumbs).
I do appreciate Safari on the iPhone compared to any other mobile device I've used. In the past, I only visited a handful of sites that had mobile-specific pages. Now, I have no hesitation about visiting any page that I would visit on my Mac. The only thing is that I don't use Safari at all unless there's WiFi to be had. Even the most stripped-down iPhone web applications seem painfully slow over EDGE - to say nothing of a site with even a moderate concentration of graphics and other elements. At least in the past if I wanted to check news stories or some reference site, I felt free to do so anywhere without grinding my teeth in frustration while waiting for a page to load. So, in this respect the iPhone is a strange trade-off.
One plus, however, is that I do find myself taking a lot more photos. The iPhone's camera is one of the best I've seen in a mobile phone. It offers surprising color accuracy compared to most phones that I've owned and it does better in low light than some digital cameras. I won't say it will ever completely replace a digital camera for me (mostly because it doesn't include a flash), but is a great camera to always have on hand. And I appreciate the ease of emailing photos or uploading them to a .Mac gallery - again as long as there's WiFi. Actually, my only beef with the camera is that you must wait for one photo to be sent before you can email another.
Overall, I'm happy with the iPhone, but I don't feel I'm as productive with it - both because of the limitations of its data service and because the onscreen keyboard is limited to portrait mode, which makes typing frustratingly slow. Then again, the iPhone is a consumer device, so maybe I shouldn't expect to be as productive with it as I should with a more business-oriented product.