Bought the 09 to replace my 05. My biggest complaints relate to interior space use usability. There are no storage spaces for things like sunglasses. The 05 wasn't great, but it has thee good storage spaces in the dash. For some reason GMC decided to go with tiny buttons to control climate and radio. It has taken me a while to get used to the new layout, but the buttons are just bad, especially if you have gloves on. I am looking forward to towing my 30' camper. The 05 did well, I hope the 09 does better.
Pretty comfortable seats, kids love the second row heated seats. I think the built in trailer brake controller will be good, but need to wait for spring to try it out with my trailer. Folding in the mirrors is way easier on the 09 than it was on the 05.
Storage space it desperately needed. The tiny buttons are just awful. I really wish I could combine my old 05 with the new 09. I had no problems with button in the 05.