I think from a comfort perspective, it's important to get a TRD package with the Sport seats (TRD OR or TRD Sport). These seats are nice, and a significant improvement over the SR5 package seats.
Before I modded my truck, I could get 21mpg on 90% highway driving. Best I ever did was 22.4 on 340 miles driven, all highway. With the bigger tires and steel additions, I'm down in the 17-19 range, worse if I wheel. The 4cyl would be better, but with the 4x4 components, not a huge improvement (maybe 24mpg IIRC).
THe 05+ saw a lot of creature comfort upgrades from the prev generation trucks. From a road-driving perspective, the cockpit is much improved. And the rear seating of the dbl cab is pretty comfortable, even for a moderately sized adult (probably not for you though). That said, it is still a mid-size truck, and you don't get all the "premium package" type luxuries you'd see in a 100-series or even a leather-trimmed 4Runner.
I've had mine for 1.5 years and 15000 miles. Other than nit-picky things, it serves me well as a wheeler, daily driver, and weekend camper.
