I've owned tons of various cars, trucks and SUV's over the years, and currently own a QX56.
My opinion on the QX56:
It tows better than any 1/2 ton SUV/truck that I've owned. The only things I've owned that have towed better are v10 ford excursion, 7.4L 3/4 ton suburban, and a few diesel trucks. All other fullsize SUV's we've had (except the suburban/excursion) have limited leg room in the second row and even more limited in the third row. The QX56 is laid out extremely well, when sitting in the second row it feels like you're in a limousine, there's more leg room in the second row than there is in the first row. The third row is also nice and roomy, I fit in there and I'm 6'1".
It has 2wd mode, auto 4wd, 4wd HI, and 4wd LO. Which is great because you can set it to 2wd mode to save on gas a little. No need for an aftermarket kit to change the entire drivetrain to parttime 4wd. The autoleveling xenon headlights have an adjustment knob where you can adjust how high/low they're pointing just incase you're carrying a heavy load and the nose of the truck is sitting high. The rear suspension is equipped with helper airbags that automatically inflate when the rear is loaded to level out the suspension.
The interior is very comfortable, is very well laid out and all controls are easily accessible. The quality of interior compared to the Armada is very noticable. When sitting in both side by side you can instantly tell that the QX56 is built using much higher quality and longer lasting interior parts/materials. The doors close very firmly and nice. The pushbutton adjustable pedals are very nice since I'm 6'1" and my wife is 5'2". The rear glass in the 3rd row is power and opens at the push of a button. The 2nd row has reclining seats. BOTH first row AND 2nd row have heated seats. The noise level inside the cabin are quieter than any SUV we've owned including our ML350. The navigation is placed nice and high and easy to glance over at.
I love the exterior styling of the QX56. It is modern, the front end looks aggressive. The rear 2 step bumper is very nice when wanting to climb up and strap things to the roof rack. The tow hitch is tucked nicely underneath the 2nd bumper step and is hidden well so it's not an eyesore like it is on most Land Cruisers.
My complaints about it:
The leather is soft, and comfortable, but it also wears quicker than more "tough" leather used in more rugged SUV's such as Land Rovers, but so far at 70k miles it has worn well and I can say it has held up better than any Toyota leather I've owned in the past. The sunroof is pretty small for this size of vehicle, they could have made it bigger easily. The memory seats are nice, but as soon as you put it into gear the memory function is disabled and won't work again till you put the car in park. That's silly IMO, if you're in a rush to go you end up with your seat/mirror settings only half way adjusted. The roofrack is okay, but could use some work. There isnt really enough support up there if you want to put anything significant on the roof. Although all the extra legroom is awesome in the 2nd & 3rd row of seats, this means less cargo room in the back when the 3rd row of seats is up. Although, even the minimal cargo room is still slightly more than in the Land cruiser's cargo area. The door panels are the same material as the Armada and seem too "plasticy" for such a nice vehicle. Same with the window switches. The frameless rear hatch glass is too flimsy IMO. It just doesn't "feel" very rugged. And finally, it takes premium 91/93 octane fuel. Ouch. Although, so did my previous Land Rover's.
If you're looking for an offroad rig, the QX56 is not for you. If you're looking for something roomy, comfortable, luxurious, and a vehicle that can tow like no other vehicle in it's class, and can handle the occasional trails, then it's the one for you.