I bought a '08 Titan in July and only driven it in town for a total of 4400 miles, with no towing. It has been back to the dealer twice for poor performance issues, mostly being inconsistent from day to day. The dealer said that this engine will not break in until 5-6K miles on it and the hesitation should go away. I finally got the opportunity to drive it on the interstate for a 1400 mile trip this past weekend back to GA where the temperature was in the 20's. I filled up with with 93 octane and with the cold temps and long trip (blowing it out), performance from 0-100 was freaking incredible, comparable to when I had a '95 Z28 with a LT1. Kicking it to pass, you had to be careful not to run into the back of the car you were passing.
On the way back, I filled up with 87 octane to save a few bucks and the hesitation at low speeds is back, switching back to 89. I found it is better to drive the hell out of it, grannying it makes it a slug.