This car is very fast for what it is. If you drop the hammer, it'll light the front tires and make smoke all day. Surprises most people who think it just has the 3.8L V-6 (which isn't a bad engine either).
The super package adds 18in wheels and larger front brakes, bigger sway bars, dual exhaust. The exhaust note isn't as harsh as the Impala/Monte Carlo SS, but is still satisfying inside the cabin. Apparently there is a 3 hp loss from this quieter exhaust (300hp vs 303hp), but I don't miss it.
The interior has too much plastic, but it looks OK. The "wood" dash trim is a special darker colour for the super model. The 18in wheels look fantastic, but steel wheels are not offered for winter tires.
The 5.3L can be hard on fuel around the city. On the highway with cruise I touched 30 mpg.
The only complaint I have is after 45min-1hr of driving, the special leather seats become very uncomfortable. The test drive is never long enough to know this, and I've made some progress in almost finding the right position, but it has been very frustrating. I miss the seats in my 1998 Olds Aurora dearly.
Overall, a sweet ride, but having 2011 Buicks pull up beside you knowing that the V-6 in them is almost as powerful as the V-8 chugging under your own hood, makes gas station visits just a bit more painful. The '11's also look pretty sweet too...