B-Man, I feel your pain. I paid about $4500 to rebuild the trans on my 2009, but I only had 73,000 miles. I was changing fluid every 25,000 miles too so it's not like I didn't take care of the transmission. I think it might have just been the TECM but the transmission shop said that when that goes, other stuff inside the transmission can get screwed up too. There's no way to know unless it is opened. They found burnt clutches and replaced that, the wave plates, torque converter, and other parts. Since I put my family in this vehicle I opted to spend the money and fix it - far cheaper than a new SUV. It shifts great now.
With that being said, GM should be ashamed that these transmissions have so many issues. My brother's Toyota has gone over 200,000 miles with just fluid changes.
2009 Enclave CX Gold Mist FWD, Bose stereo, Driver confidence pkg.