Just switched from VZW to TMO, and picked up an 8320 Curve to replace my 8830 Worldphone. After a few days of use, here are my impressions.
Size- I like the Curve's size *much* better. The 8830 never really felt right in my hand- just a bit too wide. The Curve fits perfectly.
Display- Sharper display with better contrast, I think. Everything is much easier to read.
Camera/Wifi- I actually have these things now.
Word of warning, WiFi on a Blackberry is like WiFi anywhere else, which is to say not perfect. The Curve doesn't always automatically connect to my WAP, nor does it always stay connected. However, the connection is far more reliable than it was when I had WiFi on my desktop.
Camera- I was impressed to see a camera with 5x zoom and a flash on a phone. The pictures are *very* nice compared to what I had on my Treos.
Keyboard- The keys are contoured differently on the Curve, and I'm finding I make fewer typing mistakes.
Ring volume- At last, I can hear my phone ringing! Matter of fact, I have to change out my MP3 ringtones because I had the volume cranked up on them to make up for the unacceptably low volume of the 8830's ring.
Performance- Earlier I'd asked where the extra ~$100 goes when you buy an 8800/8830 Blackberry when you don't get as many features. The answer is HARDWARE. The Curve takes longer to launch applications, and a reset takes *forever* compared to the 8830.
Call Volume- Loudest call volume is quieter than on the 8830. Not bad, just noticeable.
The Ugly: (These are mostly related to TMO Curve, I think)
The HotSpot@Home service never worked reliably for me. TMO kept insisting that it was defective hardware, no matter how many new phones I got. I tend to think the problem lay elsewhere, but since I could never get TMO to say anything but "Get a new phone", I canceled the service. With such a unique service, one would think TMO would put more effort into supporting it.
The Blackberry GoogleTalk application is unreliable. It doesn't log in quickly (or at all, at times) and it disconnects often. The automatic login does not appear to work. I will be going back to JiveTalk soon.
Also worth pointing out that I'm getting better battery performance, but this is unique to my situation. At work, I had a very, very weak VZW signal. Constantly trying to connect was draining my phone's battery at an alarming rate. I do not have this problem with TMO at work, so the battery lasts longer.
All in all, I really like the Curve. I'm a bit disappointed in the performance, but nowhere near enough to let it ruin my experience. There's just too much to like about the Curve.