UPDATE: This fix actually works, now my Nexus One is humming on 3G, you might have to reboot your phone and wait about 10 minutes.
There’s been wide complains by T-mobile users that Nexus One isn’t connecting to 3G, rather to the slower Edge network. Well, I am actually having that problem now.
Here’s a suggestion by Kevin at JKOnTheRun blog:
In “Settings,” I went to “Wireless & networks.” Look for the “Mobile Networks” option at the bottom of this listing. The next screen has a “Network Operators” section — tap it. Your Nexus One will search for compatible GSM networks in the area. Once it’s complete, you’ll see the choices, which will consist of T-Mobile and/or AT&T. You’ll also see a choice to Select Automatically — tap it and your phone should say “Registered on network.” That’s it. That’s all I did and I immediately saw the phone jump from EDGE to T-Mobile’s fast 3G network.
It hasn’t worked for me yet so I will have to keep trying…