Just picked mine up early yesterday evening from the TMO store. Upgraded from an 8100 Pearl, and I'm so far really pleased with the decision. For some reason, I didn't see ahead of time that the 1.5 UI doesn't allow for WPA-Enterprise, so I'll have to go into debug mode tonight and get that setup so I can log into the wireless here at the office. I'd also rather the "taskbar" at the bottom from the TouchWiz stuff wasn't there, but I'm really happy as well that the Cube isn't part of the default UI.
Pictures and Video are great. That LED flash will blind the folks you're taking the picture of though! Screen is excellent and I'm currently poring through the Market to find more applications.
One thing of note is the tactile feedback for scrolling and such. When the phone first did its little shake, I wondered if there was something wrong, but after using it for a only a couple of hours, I don't even notice it as something out of the ordinary any more.