I'm interested in the BoostMax as well. I see a lot of concerns over AFR, but if we look at it holistically, the EcoBoost uses a Wideband O2 sensor, so whatever PE ratio is commanded, it should technically be the same. Someone in another forum mentioned they ran a before/after dyno on a F-150 with BoostMax and the AFR stayed the same. It looks to me like the BoostMax takes in commanded torque via the accelerator pedal, and then tells the ECU a different TIP/MAP reading that forces the ECU to provide more boost (up to 5 psi).
I called Roush-Yates and JMS to see if their BoostMax units were different, and both companies said it is the same product just that Roush Yates added a sticker on their unit. If Roush Yates is putting their name on this product, then it should be good to go. Also a lot of people seemed to report about +2 MPG in fuel economy improvements, so there's a good possibility the BoostMax reduces the amount of boost at normal cruising conditions for better fuel economy.
I see the biggest selling point being that it is simple to install, wouldn't be detected by the dealer, and seems to be backed by Roush-Yates who are the principal engineers behind the Ford GT in IMSA/Tudor racing. Obviously a tune is the best way to go, but it definitely voids the warranty and for the DIY'ers, not many people are willing to give up the "secrets" or people are still experimenting with ways to defeat the torque limiters, or HPTuners/SCT still has a lot of tables locked out or missing.
I thought about datalogging to see the boost changes, but if the MAP/TIP isn't producing accurate figures, then you'll see normal numbers for boost. However, the Turbo Mass Airflow should increase dramatically.