I bought a Superchip progammer for my 2004 F350, diesel. Not an expert by any means, but I have really liked the performance enhancements, both while pulling and while without a load. Has three settings above stock, (1) tow-safe, (2) high performance, and (3) something else I never use, the middle one!! The programmer is quick and easy to use. I generally keep it on high performance because I like more power than the diesel wants to deliver at stock. Seems that I get the best fuel economy at the high performance setting too. When I am going to tow my 33' fifth wheel, I tune it down to tow-safe. Easy, and I feel fairly safe that I am not damaging the engine. 10k miles this year pulling the trailer and no problems so far.
I would be very curious if anyone pulls above the 6,000 lbs.suggested limit while pulling in high performance, and if they have had problems. Not worth the risk in my opinion, but would be nice to have that much added power under load.