I have 2008 GX and did about a year of research before I bought it. I was looking at Highlanders (wife's idea - barf) and a limited V8 4runners. For all intents and purposes, a GX is a 4th Gen Runner. Same crappy calipers that seize up, same zerk fittings to lube the driveshaft, etc. Good luck trying to tell people that though, they just see lexus and wont get it. The big differences are in the interior. Most GXs come with the Nav system which also includes the Mark Levenson stereo. A BIG FYI - it is a 8ohm speaker system so you can't just call crutchfield and drop in new ones. These speakers will eventually have their cone tear. Best solution seems to swap cones or some other voodoo to bring it back to life. If you find one that doesn't have nav, it has standard car speakers and you can put whatever single/1.5/double din player you want.
**In line Edit - there is now an Apple Play plug for about $600 to add to the stock nav. Other owners have swapped non-nav center controls into nav GXs as well **
Also most GX come with a third row. I like it but it folds up in a kinda odd way.
Another interior quirk is the center console. It isn't the stacked/sliding usual toyota design. I call it the missile silo cause it looks like the ICBM launch doors on some Nebraska prairie.
You will read (what I feel) are a lot of overblown concerns/panic/whatever about the GX suspension. In addition to the rear air, the 4 shocks are magnetic ride. You have a switch in the cabin which you can choose the firmness. These shocks will eventually leak. Also those rear airbags will eventually leak as well. Some people go all in and replace both shocks and airbags with OEM replacements. I think it runs something like $3k. My plan when this happens in the metaltech mounts for actual springs in the back pair with some 5100s. In the front, I plan on going all out with some Icon coilovers.
I think the GX is an awesome truck. Totally capable off road, plush interior and some real character - what other vehicle has nav, backup, barndoor in the back and a cassette player? Not only that but you will get a lot of complements on it, especially if you get a nice color combo (mine is dark blue with tan interior).
PM if you have any other questions.