Extensive compressor reviews and FAQ

Mad Professor Forest Green: This pedal is based on the BJFE Pine Green. Bjorn of BJFE can only hand-make a small number of pedals each year, so he has arranged with Mad Professor to manufacture his designs on a larger scale. The MP versions are not 100% identical to the BJFE-made ones. There are two versions of this pedal available: PCB (printed circuit board) and "hand wired" (all the parts wired directly together like spaghetti). Some people believe hand-wiring sounds better than circuit boards... but some people believe the Earth is flat too. This review is of the hand-wired one, for what it's worth.
The tone is quite transparent. It doesn't lose any highs or lows, except that the "Tone" knob rolls off the lowest end, and tightens up the lows and mids, as you turn it to the right. So the most bass-friendly and transparent setting is with the Tone fully to the left; but the higher Tone settings will be good for somebody who wants to rein in a muddy or boomy instrument tone.
The "Compr" knob appears to control the amount of pre-gain boost into a fixed threshold. So turning it up is the same as lowering the threshold (increasing the amount of your signal that gets compressed), and it also adds a bit more of the coloration and "zing" of a clean-boost pedal.
The MP makes one huge improvement over the BJFE: it has a switch to select between a very high ratio (labeled "compressor") and a very low ratio (labeled "sustain"). With the switch set to "compressor", the most natural and generally useful Compr knob setting will be at the leftmost end; but at higher Compr settings, you can get a wide range of extreme squash and sustain effects. It doesn't do such a good job of limiting big peaks though, so it's not suitable for slappers. With the switch set to "sustain", the entire sweep of the Compr knob is useful, just adding different amounts of light-to-moderate compression.
The noise level is fairly low overall. At the high threshold, high-ratio setting there is hardly any noise at all; but at the lower thresholds and low ratio setting it can get somewhat noisy. Even then it's not terrible though, no worse than the Keeley or Barber for example.
It's the same small (MXR-sized) box as the BJFE, but the paint job is more professional. It's not the most rugged paint out there, but it's not going to flake off as easily as the BJFE paint does. The footswitch is true bypass, and it runs on standard Boss-type 9VDC.
While the tone and noise are only a little bit better than the "cheaper" competition like the Demeter or EBS, the versatility provided by the comp/sustain switch makes this pedal much more useful for different styles, and goes a ways toward justifying the price if you go for the hand-wired one. The PCB one is a better deal all around.