May I distill this down in a nutshell? For those who think this "tune" is going to give them a few extra HP (and perhaps better shifting) and not void their warranty- they have a point, and I get it. For those who think that 30 HP is not worth the amount of money over a tune that could provide them a lot more HP (and perhaps better shifting) at the same price point- they have a point, and I get it.
However, if you believe that if you "pop" your engine while on the Ford tune the dealership and warranty service guy are just going to "pop" for the repair, good luck with that! Just because they say it doesn't void a warranty, unless you find a nice dealer who needs the work; and that work pays well, you're going to be out of your vehicle for awhile.
However, if you're on the stock turbos- neither the Ford tune nor a dedicated octane ZFG tune should cause any worries. I hesitate to include other tuners simply because looking at their dyno maps, they are not addressing the boost spikes around 3K RPM which can lead to detonation problems.
The biggest concern with a dedicated octane tune is when all of your correction maps are on (say) 93 octane gas. You, your pal, your high school son, etc, decides to fill it up with 87 to save money on a dry 30 degree day and then decides to make a WOT run. That is a recipe for problems.
In the end, I don't blame anyone for wanting a bit more HP so they can say they're tuned and they believe they're keeping their warranty intact. It's your money after all.