All around excellent vehicle. 4WD system is fantastic and they look great.
Tires and rims are kind of an odd size which will somewhat limit your options for replacement or winter rubber.
I have been hand calculating the fuel economy and I get approx 18MPG in the city and 23MPG in the highway. The truck is still breaking in and I just just changed the oil to synthetic, so I believe it is possible to still improve 1MPG or so. These numbers aren't fantastic, but just as good as some "car" based SUVs like Subaru's and even Toyota's Highlander.
The V6 is very torquey and entirely adequate for the vehicle. The only reason I would consider a V8 is if you are towing a large trailer often. Also be aware that if you select a V8 4X4, the transfer case is automatically the "inferior" Full time transfer case. the V6 transfer case give you the option of full time if you desire it, in addition to a 2WD mode to save a bit on fuel economy and wear and tear. It boggles my mind as to why Toyota doesn't offer that in the V8.
Only other possible design flaw that comes to mind is the transfer case has no Neutral setting.
These vehicles are not cheap, but they hold their value exceptionally well and are amongst the top rated vehicles you can buy (car, truck, whatever) for overall reliability.