If anyone is having 3G issues on the Nexus One, the following may help:
Does the Nexus One Have 3G Problems? - Android - Gizmodo
Spotty 3g? - Google Mobile Help
I am unfortunately returning mine because of having nearly nonexistent 3G and 1 - 2 bars of voice where TMO says everything should be perfect.
I don't have time to wait for HTC and TMO to point fingers at each other. I'll wait for the VZW version.