Thoughts from the converted.
I was a naysayer, ranting on about how I hated the lock in, and how lack of HSDPA would be a pain, etc, etc. But having played with a friends for a bit and first testing to make sure that it's Bluetooth worked with my built in car kit, I took the plunge and got one last week. It was worth it.
I was on an over priced plan at Orange for the number of minutes I was using anyway (my fault really) so £45/m at O2 will be a cost saving. And I've discovered that the iPhone user experience is just not given justice by any of the reviews I've read. It's so slick, and the level of calendar and contact synchronisation with my MacBook has given me a noticeable productivity boost.
Text entry is also much much quicker than before. For me, the trick is to peck at it with one finger. I don't know why all the pics and demos seem to insist that you have to use two thumbs, as being the biggest digits you have they just get in the way and are more prone to touching keys you don't want. On my old K800i I had to use thumbs because the keys require a certain amount of force to be activated quickly. The iPhone doesn't suffer from that, so you're only limited by how fast you can tap. After a bit of practice it becomes like touch typing; and though mistakes creep in, the iPhone's error correction (for me) is about 95% accurate. Once you learn to trust it, you just don't slow down and let it do it's thing. It's not as fast as typing on a keyboard, but is way faster than any other phone I've ever used.
I also like the fact I can do stuff around the house while listening to my music or an audiobook and not worry about missing a phone call because I couldn't hear the phone on another room.
Carrying 400+ wedding photos around in my pocket all the time has proved to be a real boon too. I've always got them with me friends want to take a look.
There are some things I'd like to see improve a bit, but I'm sure that Apple will address those in time. And I expect that this time next year I'll be looking to upgrade to a much more capable device.
As for the usefulness of EDGE, I can't say yet as I've not done that much traveling with it. Email doesn't seem to be much of a problem as I've got it syncing once an hour, and I don't care how long it takes to download an email as I'm not being charged per minute. At home over my WiFi, it's very quick. And browsing with Safari is so much more usable than I expected. I used it to book a couple of film tickets via the web the other day.
Would I give it up having had one for a week? Not a chance. It's too much fun and I'm getting too much value out of it.