A good number of you likely will be buying the Google Nexus One unlocked for use on AT&T's network. Obviously, you'll be missing out on 3G. And some of you have asked about plans and the like. We reached out to AT&T for its official position on unlocked phones, and here's the response:
“Wireless is a fiercely competitive industry, and we aren’t at all surprised that others are responding to our leadership in smartphones. Twice as many smartphone customers have chosen AT&T over any other carrier. We have always allowed customers to bring any unlocked GSM-compatible device for activation on our network under a pricing plan. However, if a device has not been certified for use on the AT&T network, we can’t guarantee their performance and the customer is responsible for handling any device-related issues that may arise.”
We'll go ahead and say it so you don't have to. AT&T has plenty of problems supporting at least one phone that has been certified for use on its network. So, it's not like your Nexus One (or any other unlocked phone, for that matter) will wither and die if you use it on AT&T. Just don't go asking them for help.