An absolutely silent, full-throttle sprint--in reverse--for about fifty feet.
That's the first thing I did after belting into the Tahoe Hybrid, after, of course, making sure that no people or cars were moving on the empty level of the parking garage.
I did the reverse stomp to help personally verify that the Tahoe Hybrid's gasoline engine propels the vehicle only when it's moving forward, leaving the electric motors to power the vehicle in reverse. It's true, because, as Joe DeMatio pointed out in his green-SUV comparison story in our April 2008 issue, "GM's two-mode transmission doesn't include a reverse gear."
But except for those who have to back heavy trailers up crazy-steep grades, the Tahoe Hybrid may be just the ticket for earth-conscious people whose big families and cases of stuff rule out even the largest minivans and crossovers (especially now that diesel fuel costs so much more than gasoline).
From behind the wheel, I found that the brakes felt very artificial and squishy under hard braking but fairly normal during regular, light applications. Foot-to-the-floor acceleration is weird and rubber-bandy, because the hybrid assistance alternates between helping and bailing.
I do like the Hybrid-specific lower front fascia that resembles a tasteful body kit, but it seems that this would be a liability when traversing boat launches and so forth. The hybrid display screen isn't as clear as Toyota's, either, but at least it gives you an idea of what's going on with the drivetrain, unlike GM's Saturn Vue Hybrid.
In spite of the Tahoe Hybrid's 20 mpg city/20 mpg highway EPA rating, the trip computer told me that I got only 17.5 mpg for my 37-mile round-trip commute on mixed roads. Still, that's a few mpg better than I get in similar big trucks.
I wouldn't buy a big SUV like this unless I had a heavy trailer to tow, however, and I'd have a hard time getting past that electric-only-in-reverse issue.