It depends on what you want to haul in the bed of the truck. I didn't get the HD payload and have no regrets, but I don't haul a lot of stuff in the bed of my truck. My truck has a payload of 1794 lbs. and the only time I weighed, loaded for camping (with a trailer of about 6500 lbs) I was well under on all capacities.
Now, for how it pulls: In a word, WONDERFUL! I just returned from Colorado and New Mexico and it amazes me how effortlessly it pulls hills. This trip I didn't do any of the 11,000+ passes, but we did get up over 10,400 and it was no sweat at all. The thing I really like is that so much power is available at less than 2,500 RPM. On the highway, you can just set the cruise and listen to it hum, rarely will it shift down to 4th gear.
Regarding fuel: Earlier this year, I used almost all 89 or better octane when pulling, but ended up with a tankful of 85 one time and could tell no difference. This trip I never bothered with higher octane at all, heard no pinging, had plenty of power, and fuel mileage was about the same 10 mpg average as usual. In fact, for the 150 miles or so downhill miles from Santa Fe to Tucumcari on the way home, she registered 12 mpg. I was grinning from ear to ear!