I recently purchased a 2009 Sierra Hybrid, 2WD truck. My initial impression is that this is a great vehicle. I have all of the standard features of a Sierra with gas mileage averaging 21 MPG combined City/Highway. Outstanding! Contrary to Expert reviews, I would not agree with assessments that transitions shifts between electric and gas as seamless. On the contrary, these transitions can be felt-- abruptly in some instances. I also have concerns regarding the transition between regenerative and hydraulic brakes. In some instances, my brakes have actually disengaged momentarily making me feel as though I might roll into the vehicle in front of me. A very uncomfortable feeling.
(1) Gas mileage: outstanding for a truck; (2)Exterior: especially relative to Silverado; (3)Ride: very smooth; (4) Interior Noise: incredibly quiet -- perfect for cell phone conversations.
The disengaging brakes feels like an accident waiting to happen and clearly needs to be resolved. I also believe that more work can be done to smooth transitions between gas and electric. And finally, allow the truck to enter or stay under electric power when going downhill at speeds greater than 30