Here's my opinion on Rev-X...
For several years now we've been offering modified FICM strategies in order to help restore the lost performance and fuel economy of 6.0L's that have been reflashed by the dealerships. You've heard the story 1000 times... Someone goes to the dealer for something and drives off the lot immediately knowing there's a problem. Performance is down and after driving for a while, they notice fuel economy is down as well.
The other problem is that Ford has been using inductive heating strategies for 3-4 years now, as a means to resolve the "cold start" issues caused by injector stiction. The original, aggressive strategy works by superheating the spool valve which loosens the oil. This had the unfortunate side effect of damaging some of the solder joints (and in extreme cases, circuit board traces) in the FICM and eventually caused voltage drop and no-starts. Later FICM strategies have a milder inductive heating strategy which draws only about 15 amps, instead of close to 30 amps.
We originally started using non-inductive strategies for updates because they would help prevent the hardware issues caused by the inductive heating strategies. Of course, this would occasionally have the nasty side effect of (re)introducing a cold start issue on vehicles, particularly those in cold climates. This forced us to develop the hybrid strategies which still used inductive heating (the later, mild strategy) and blend in the performance characteristics of the earlier strategies.
Our goal would be to not have to use inductive heating at all, but spool valve stiction is a very real problem and too many trucks simply will not function at all without the use of some form of inductive heating.
With that said, we have been following the Rev-X posts very closely because of the claims by many forum members of the immediately noticeable improvements in starting and drivablility on their 6.0L. Several of our FICM customers have used Rev-X and noticed similar improvements. Here is an example:
One customer had just recently converted his FICM to one of our calibrations. He originally tried the non-inductive strategy, which immediately was apparent that it would not work as the truck would barely run when cold. Switching to the mild inductive heating strategy offered a mild improvement, but he was STILL having problems starting and running when cold. He ended up returning to the original inductive heating strategy until we could build him a custom FICM program. We were in the process of building a strategy to include the aggressive inductive heating when he contacted me to give me an update. He said that despite the protests of his father that Rev-X was "Snake Oil" and a waste of money, he bought 2 bottles and poured it in his truck. No oil change... just straight in. After 15 minutes of running, he already noticed a change in the sound of the engine, which appeared to be noticeably smoother. He reprogrammed his FICM back to the non-inductive strategy and noticed that his truck ran considerably better, but still had some minor cold issues. Switching to the mild inductive heating strategy, the truck ran perfectly with no cold issues at all. This is the calibration he's chosen to stick with.
Time and time again, Rev-X has shown to be everything the manufacturer has claimed and every single customer of our that has used it has noticed immediate benefits, particularly in conjunction with our FICM strategies. I'm still waiting for mileage reports from customers, but all indications are that with smoother injector operation, there has been a noticeable improvement in fuel economy.
I would say to the one individual that didn't notice any improvements when running Rev-X, your injectors may not have been a significant problem so Rev-X didn't provide you with any real benefit. You may find that changing your FICM and/or ECM strategies might provide a much better benefit to performance and fuel economy.
To date we've had about 2 dozen customers (that I'm aware of) that have run Rev-X, with and without our programming, and every single one of them has had a positive experience. I don't recommend very many things as I am an extremely skeptical person by nature, but the number of positive experiences by customers is overwhelming.
I hope this information is helpful.