This may not be an issue for many people, but we did not have our contacts imported into Gmail. And on a Nexus One, unless you want to enter all the contact manually, this is pretty much mandatory,.
Fortunately, the importing process is simple:
Log in to your Gmail and go to Contacts, then click on Import (right hand top corner)
We were exporting from Address Book on a Macintosh, which supports the vCard method.
Go to Address Book, click on one contact and then select all (Command +A).
You can go to file and select export vCard on select contacts…
or your can right mouse click on selected contact and select export vCard.
The last step is to select the import file from the Google Import screen.
If you have a lot of contact it may take a few minutes.
If you have your Nexus One connected to your Google Account, and Sync is active, the sync process will start almost immediately.
The whole process took less than 15 minutes.