That's funny, since I bought mine last year, I was trying to see on different forum what people were thinking about it... without much luck.
When I first tried it, I was floored. I was originally looking for a 2 channel overdrive that would sound like a second channel from my Laney LC-15R. I quite like the slight fuzz this amp produced with the gain cranked. So I was basically looking for a LC15R in a box providing 2 extra channels.
The FOD gave me exactly this, to the difference that one channel is a clean fat boost instead of an overdrive. All for the best really though.
I think the first thing to say is that this pedal is very transparent, while giving a good quick in the bottom of your amp.
The clean boost is just magnificent. It fatten the sound and no matter what the settings are on the amp or on the FOD it always sound great.
The overdrive fattens thing an extra notch. Tone pot very sensible, no extreme settings at each end of the run. With the gain kind of 2/3 of the way on the bridge pup I get raw raunchy classic rock sound I really enjoy.
Unfortunately for me, if I go further with the gain or switch to the neck pup, It gets muddy quite easily. I do now believe that it is because of the amp, and most probably because of the speaker, which basically get pushed too hard in the low range by the FOD and looses it completely.
Hence my next move in gear acquisition will be a new speaker to prove or break my theory. But from I have read in other thread about the LC15R I think I am on to something.
Anyway, the FOD is quite pricey, but itwas giving me exactly what I was looking for, 2 extra level of gain/boost (3 when you get both boost and overdrive on) that are true to my amp... As I said, so true to it that it busted its shortcomings! So I can't encourage you more to give it a try.
I think Jazz Rock summed it up nicely. This is a GREAT pedal in scheme of things. Very versatile (germanium and silicon switch) and the Fat Boost Control alone is one of the best Fat "Type" Boosts I own (and I own a Klon, Tim, original 808, etc...). A very satisfying pedal for lead work. It's very expressive and vocal. Some settings can get a little muddy on the lower strings, depeding on the guitar and your amp settings. All in all, a super musical and fun pedal to play.
yes this is a very underrated pedal - Im prejudice as i painted many of the first batch .... but its a very useful pedal but it doesnt do crazy fuzz stuff so I think it gets overlooked as a vanilla workhorse , but between the sili/germ switch on the side and the input gain trim (the whole on the side) its very useful ...
(oh and if yours feels too saturated turn that little internal trim in the whole on the right side)