Traded in my E90 '08 6MT last fall for an E90 '11 DCT. It was a March 08 build with 38400 miles when I traded it. I was the only owner. Transmission was replaced at ~15K miles due to excessive grinding in the 1-2 shift. Tracked once. The new one will definitely see more track time. Oil was changed every 7K miles.
I'd probably still have the '08 except for a worrying amount of bearing material that showed up in the last few oil reports. When the last report said "keep an eye on your oil pressure" I decided it was time to move on to a newer vehicle. It was still running strong and not making any noises but since I was planning to throw a few bolt-ons at it I didn't want to run into any warranty problems if it decided to grenade on me.