The QX56 only has a V8 engine available. It's a big 5.6L, and the only transmission paired with it so far is a 5 speed automatic. Unfortunately, those factors, and this SUV's huge size, contribute to the 10 mpg mileage on this vehicle. With gas prices the way they are, don't expect to many people to be stretching their budgets to get into one of these.
The QX56 only comes with one trim line, but it is fairly loaded as we should expect from a luxury vehicle. Some of the standard features include a ten speaker Bose system, DVD based navigation, and 18 inch alloy wheels. Upgrades include a DVD entertainment system.
One thing this vehicle does have going for it is price compared to competitors. The Lexus LX is more expensive despite lacking in many features.
These SUVs are rare on the used car market. You won't find them in your local car classifieds, but you might find one on Craigslist. You've got your best chance of getting one used either going to an Nissan/Infiniti dealership where you'll pay a stiff markup, or by looking at the listings on eBay auctions.