As the title says this is not a typical distortion pedal.
I use it with a '67 Deluxe Reverb to push the signal a little more when the amp is on the verge of overdrive, i.e. where the good things start to happen soundwise.
If it's not a distortion pedal, what is it?
A: It's obviously an attempt to make your amps sound like a Dumble.
B: It will give your sound a slight compression and a slight distortion, like when you push a classic 60's/70's amp a little - i.e. LOUD!!!!!!!
C: With a typical Strat you can approximately double the signal hitting the pre-amp.
Pros: I've never heard a Dumble in real life so I can't comment on how close it is to the real thing, but judging from recordings of Robben Ford etc. I'd say it comes close.
Controls are straight forward.
Cons: It might take some time to fully appreciate and dial in the way YOU want it to sound, thus it's not a pedal that everyone "needs".