I test drove the SUT and thought it was great.
I think that I would miss the space to pile my kids and their stuff, however, the SUT does have a cover for the back and it would be handy for hauling stuff. (trees and plants.)
I would miss my Sunset Orange though. The back seat should have enough room behind it to fit a narrow box. We have one in our F350 with a 10" sub in it. The local stereo shop helped me out. Enjoy your new Hummer!!!