I've been very happy with Dustin's tuning at Diesel Addiction, after my injectors he sent me a tune for my truck (back when I lived in Oregon) and the tune was great, pretty much spot on for not tuning the truck in person. Now that I am in GA he was able to revise the tune in person and make it even better.
Rob has a good rep and does great tuning as well. I will say though, I tuned a friends LBZ dually with one of Dustin's tunes and he was very impressed. He had been running Robs tunes and liked Dustin's tunes better esp for towing, granted both sets of tunes were made with out the tuners seeing the truck.
If at all possible having the truck tuned in person is better, because every truck runs a little different and will respond to tunes differently.