I just used my '09 TRD as intended, by hauling a heavy load.
We went through the scales on I-8 just east of the CA/AZ border. Gross wt was 5104lbs, unladen wt. per DMV is 3625lbs. After subtracting for myself, passenger and luggage, we had 1165lbs of auto parts in the bed. Truck handled great (I do have Hellwig 550 helper springs and don't have the upgraded TSB spring package) and didn't bounce off the rubber stops once.
Very happy with the performance and capacity of the truck.