I'm really happy with the unlocked Curve I bought from GSMPhonesource, build quality and all seem fine to me.
The one warning I have to you guys though is that T-Mobile is having issues with the Curve's service books. I'm not sure why, but there were issues getting the correct service books sent. I've resolved most of the issues and have access to email and the T-Zones browser, but still don't have the regular browser shortcut. T-Zones does the same thing, it's just slightly aggravating to have lost the old "B" shortcut.