What are you talking about the engines aren't great? Variable Valve Timing, Displacement on Demand paired with a six speed automatic that everyone's been wanting, I think will be plenty good. You can't look at horsepower numbers on a truck to tell the worth of the engines. The torque is where it's at for trucks, and that, for whatever reason, was not given. And they have a 400 HP engine available for the higher end of the spectrum, so where's the problem?
These things look like a homerun, even in spite of the gas prices. The old ones were rated at 16/20 (for the 4WD version), not bad for a full size SUV (best in class). And with the new ones fuel economy improved, it will be getting better gas mileage than an Xterra, Explorer, or heck, even the outgoing Trailblazer. Not too shabby a feat.
I can't wait to see hi-res pics of the interior. These that are out now look great, but are too small to see all the details. And, remember, these are in the trucks, which have traditionally been the basment of GM interiors. They've promised the next generation of all their vehicles are going to be at the top of their class in interior quality, and while I've believed them, there have been a lot of doubters. Perhaps this will erase some of that doubt.
And one last thing, decent chop of the Avalanche, but you forgot two major things, the buttress coming off the back window to the bed and that it is based on a Suburban, so the bed needs to be longer and the door line needs to go straight down, rather than have the wheel well pertruding into the door.