When I bought my 00 GT used last june, my TOB started chirping after a couple weeks. It got worse, and I finally replaced the bearing. All was well for several thousand miles, then it started coming back lightly, and eventually it was back to the way it was. Funny thing is, sometimes I do hear it chirp, but its actually gotten better after it got worse, so I really dont know what the deal is.
I have also noticed that alot of people talk about greasing the bearings during install, but for the OEM bearing it specifically says in the factory service manual not to lubricate the bearing because they are already lubricated from the factory. When I pulled mine out of the bag, it certainly wasnt bone dry, but I dont know.