Toyota doesn't rate their pickups in half or 3/4 ton. If you get the 5.7L, it has the towing capacity of everyone else's 3/4 ton though. I have a Tundra with a 5.7L and love it. I went with Toyota because of great success stories I've heard from every one I know that's ever owned one (Tacoma and Tundra). Two years later I'm not disappointed. Usually I would be ready to trade by now but I still love it. I bought it new and have 62,000 miles on it in 2 years. I'll probably drive it till the wheels fall off.I am pretty sure yours is not a 3/4 ton. I do admit the Tundra looks pretty big for a half ton though.
I have a 08 Tundra and a 99 Tacoma. Honestly I like the Tacoma way better than the Tundra. My Tundra has the small V-8 and it averages around 17 mpg on the highway and its a 2wd. You are correct that the small engine does have plenty of power. If I ever buy another Tundra I will go ahead and get the big 5.7L engine and 4x4 since it appears those options don't affect fuel millage much.