Seems like a nice phone for sure. I'd like to see a slightly larger display to take advantage of those fast internet speeds, but still seems solid. Speakerphone is a bit lame from what I understand, but as long as you aren't always on conference calls using it I'm sure it's fine. I don't personally like the "Espresso" User Interface that they use for this line, but other skins like launcher pro would take care of that. I'm sure that it's slated for a Gingerbread Android update, although since it was just released with 2.2 it make take a while compared to phones that have had 2.2 for a while. Wifi voice calling is a sweet feature if you don't already have unlimited minutes or if your home coverage isn't overly strong.
If you haven't looked at the new Windows Phone 7 devices then TMo has the HD7 which is a bit of a monster.