I used to have the SAFC-1 - now I have the SAFC-2.
With the SAFC-1 I gained about 5hp/5tq, "butt tuning" on a dyno. I didn't have A/f capabilities (not hooked up to a wideband o2) and this was a tread dyno. I didn't maximize use of the hi or the lo - i just wanted it out of the lean condition I had in my SVT. I did about 8 runs on this kind of dyno and settled for those settings. (I paid about $100 for that, but that was a hook up)
I bought the SAFC-2 mostly cuz it looks cooler. But it does have some advatages over SAFC-1. SEARCH here and on the net - there's an abundace of info on it.
I am dynotuning my SVT on a chassis-dyno come May. Looking for 185-190fwhp on a 2.5L
With the SAFC-1 I figured out about 2 different settings I was happy with - one gave more torque and the other more hp. With the SAFC-2 I can switch inbetween programs. Stazi has my SAFC2 right now - he's figuring out the new wiring (it's essentially the same except for some new goodies).
You cannot turn the SAFC off as it is now essentailly part of the ECU.
On cost - a nice chassis-dyno probably would run about $100+/hr plus install of the bung for the wideband o2. Tuning generally takes anywhere from 1hr to 3hrs.