In some circles this pedal is over hyped, in others it's not appreciated.
People seem to think it's just another tube screamer clone. And it is, even though it has adjustable bass and treble, rather than just a tone control.
They're cheap, which is a bonus, they sound good out of the box. Also good, since the components are surface mount and not easily modified. There are some "secret" bass mods out there, but if you're handy with a soldering iron and can do simple R/C calculations, you'll be able to do the mod for yourself.
One was made in USA and the other in China.
There are no sonic differences to my ear, but there are some visual differences.
Namely the colour of the capacitors and from memory, the PCB's might be a different colour too (it's been a few years since I opened them up).
The sound of them is a mild overdrive to a very moderate distortion. Two in series is pretty good for a metal distortion tone. The distortion never cleans up completely, so they're not any good as a clean boost.
It could probably be changed, but the traces and parts on the board are tiny and I doubt worth the effort.
Even though this is an overdrive pedal, that's not really what I use it for.
It turns out that Digitech have incorporated into their pedals, a very nice DI, complete with the correct EQ to record the guitar clean or distorted through the "mixer" output. It balances the tone and simulates the reactive load of a speaker. I use it all the time when noodling with my headphones on or recording guitars when I can't mic them up (which is most of the time). Actually I like using the Bad Monkey in bypass mode to act as a buffer and signal splitter, so that I can record the unaltered guitar tone through the desk as well as recording an amp. That way I can change my tone/fx later and if I want to re-amp the signal for re-recording "live" effects.
You should be able to pick up a bad monkey for about $50AU.
While there's nothing ground breaking going on, they offer some very handy tools for the recording guitarist.
I've even used them live when there weren't enough Mic's available for the whole band!