I was thoroughly impressed!
Just got this truck about a month ago and this is the first time we've gone across the pass to Leavenworth, WA. It's a two hour drive from home, sea level to 4500' Not the steepest by any means but the V6 took it with ease.
Until the steepest part, last couple miles to the top, I had the cruise set at 65 and it had no problem maintaining that in OD. I think it shifted down to 4th twice in the 40 miles or so to the top. For the top climp I kept it in 4th and held 65-70 without any issues.
Had me, 6'2" 250, my wife and two kids with their ... 6 or 8 freakin bags. Probably 450 total.
The trucks feels great on the highway but I expected it to have to work more to pull us up the mountain. Definitely not my dads Toyota (pre-tacoma trucks).. great trucks but no power.