T-Mobile G1 Users Having Data Activation Problems?

At least a few people who got their T-Mobile G1 in the mail today—one day before the official launch—are having issues activating the data plan with their SIM card. One person was told by customer service that they simply couldn't use it until tomorrow, although T-Mobile PR has assured us that's not the case, and that anyone having problems should try turning the phone off and back on. Failing that, hit up customer service, though it doesn't appear to have been too helpful in Andrea's case. Have any of guys been had data issues? [Android Forums]