I was talking to my dealer service writer today and he mentioned that several TTs have had their rear end go bad, and that the repair was roughly $4-5K. I had not remembered anyone on this site having this problem. Have I missed any?

had a few Haldex controllers go bad, although not many of those either...one post the other day said the dealer said you had to replace the rear end when you did a controller at 4K-5k cost...which is complete BS....

Usually the result of abuse. Leaking diffs and broken Haldex units means a vast ammount of money needs to go on repairs. However, I've never ever seen a rear diff or Haldex clutch being repaired at the dealer. Audi pays good money to the dealers for warranty issues so most just swap them for new parts.

replaced under warranty AND the final rear drive was replaced as well.
The haldex oil, as described to me by tech, was burnt and full of clutch pieces. I have no reason to believe the final drive was bad but it was replaced as a tandem working piece, according to dealer....I was told the cost would have been $4k.
My work order is still open at dealer pending delivery of hatch trim and new dash, also to be replaced.

I reported here that I became aware of audible rear wheel rumble while turning either left or right at low speeds; especially evident while applying torque(throttle) during said turns. This first experince came at about 17-18k miles.