This is just my opinion: Unless you have a pretty good idea of what a mod is going to do FOR you and what the possible drawbacks are (and how easy it is to "reverse"), I don't think I'd try it.
I know, how does this "square" with getting a "tuned" truck from PHP? Well, for me, it was:
1. I hated the way the truck nosedived when I wanted to pass someone.
2. I thought it SHOULD get better gas mileage than it was getting.
3. Several people had made posts saying the Edge programmer made all the difference.
4. I had read MANY posts from Bill in f150Online and then I TALKED to him. (And our talks covered things other than "tuning".) This lead me to TRUST him!
5. Finally, I knew I could "reverse" things immediately if I didn't like the result and I'd only be out $400.00 (approx). (Sometimes, you just take a "chance" - its only money!) 
So anyway, this was the "soul searching" I went through before buying an Edge that later got converted to a Gryphon. I've never regretted the move.
So, how do you feel about Dynatech? Do they seem like "upfront" people? Are they warning you about possible damage to your truck? Do they seem to be in there helping other people using their products? If you don't have a "good" feel about this, don't go there.
- Jack