When I decided it was time to move up from extremely capable and built Xterra I went with the Tundra and haven't looked back. (Well, the only time I look back is to see if the travel trailer is still there because in all honesty the truck barely notices towing it).
Everything involves compromise and I was prepared to make that sacrifice in giving up a smaller sized rig (the Xterra) that would likely go some places where the Tundra won't (easily) for the added room, comfort, and that awe inspiring 5.7 litre powerplant. I don't think I could ever go back to a mid-size vehicle after spending some quality time with the Tundra.
I purchased the TRD OffRoad option, not the TRD Pro, as it was my plan to set it up suspension wise myself. I have (sitting in the basement ready to install in 2 weeks) ADS Racing remote res coilovers, piggyback triple bypass rear shocks, MCM Fab uca's, Dakar leaf packs, Firestone airbags, and a set of Method wheels with Nitto tires.
My Xterra had a 4.o v-6 that provided very respectable power, and this Tundra's motor is simply head and shoulders above that power wise. I am not one to hammer it down everywhere, so I find mileage works out better than with my old Xterra. I've off-roaded it totally stock and so far have been very impressed. I will be locking it at some point down the road. The mid-size platform served us well for years, but our idea of where we see ourselves adventuring, and how we get there has changed (hence the appointment with Four Wheel Campers on Saturday) so a full size reliable truck was something that I knew I was going to want. Everyone's wants, needs, and goals are a little different so I'm not sure if the full size rig is where you want to be, but for me it's been a great decision. Have i mentioned the power yet?