I have a 2010 4.6. My thoughts:
Go 5.7. The 4.6 is ok but really does not do better on mpg based upon what I read about. My 4.6 might pull 22mpg in summer if I do lots of work; it is nothing to drop it to 16. I never drove the 5.7 but others say it is night and day.
That said, I find tip-in excessive on mine; forget about winter driving without snow tires. The primitive 4x4 system means you can only use 4wd when it is dicey; no proactively engaging it. THe driveline binding is right up there. No full time AWD option (center diff unlock). I found a FWD with all seasons is better than a Tundra with snows; the FWD has a clutch and can be properly feathered, and is very predictable, while the Tundra is stuck in RWD and tail happy.
Also, I find mine likes to downshift for hills. I guess that is ok--but it'd be nice if it didn't. I have the towing package, which comes with better rear gears; I cannot imagine a 4.6 with the regular 3.9:1. Sixth would not be usable. I find it likes to unlock the torque convertor long before downshifting, and it irks me to no end.
Historically the front diff likes to go; that might be fixed by now. Steering racks, cam tower (oil leaks), air injection pumps and possibly wheel bearings are other trouble spots. Low mpg is often reported. 8qt sump takes 0W20 (or whatever you want to dump in); to remove the oil filter you must remove the skidplate and then use a fancy oil filter socket.
Brake pads are easy to do, but so far I am finding short life on mine. I suspect rotors will be expensive. Have not pulled one yet to see how much of a job that is.
I find the steering is very light; it takes a fair amount of concentration to drive this thing. Either it wants to downshift, or wants to wander if you look away for a nanosecond. Let alone parking...
Payload used to be real low. The refresh upped those by shedding a couple pounds iirc, but the 4.6 oddly lost towing capacity. Which makes me think they were optimistic the first time.
After that there is the typical complaints: too tall, too big, too high off the ground, tires too big... the same complaints all other full sizes get.