So, I spent a little time with the pedal today. Directly into my Archon, and I set it at unity gain (or as close to it as I could get). I decided to record what I did with it because I think that will give you a chance to hear what it's doing and we don't have to worry about what we mean when we try to describe a certain aspect. I used my 594 SC, playing fairly delicate picking in single-coil mode on both pickups, then light strumming. Then switched to humbucker (I think I noted this incorrectly on the SoundCloud page) and did heavier strumming. All on the clean channel. Switching to the dirt channel, still in humbucker, some heavier chording, then a couple solo licks. Guitar volume was on about 7-8 for all except the last, when I turned it all the way up. For each of those, there's a clip with the pedal bypassed, then the pedal with compression at 0, 9:00, 12:00, 3:00, and dimed.
As far as coloration, I don't hear any. The guitar sounds the same to me when the pedal is bypassed and when it's active, minus any compression. It's very transparent to my ears.
As to how it compresses, this is a tough area. As
@shinksma alluded to, there are no attack/release controls, so you gets whats you gets. I didn't specifically try to dial in a clean, country-ish, chicken-picking stereotype compression sound, but I didn't hear it, either. Not to say it's not there, but I didn't hear it with what I did. It's a very smooth compression, which is probably to be expected since it's based on a studio unit. Overall, I like what it does for my sound. I can see instances where another compressor might serve a different situation better, but by and large, this thing would be good in most situations.
Now the noise. I'm not going to say it's true on every pedal, but I do hear a bit of noise introduced when the pedal is on. Going through the amp, I discounted it - I sometimes get noise from suspected interference or whatever the conditions of the day are. But at the very end of the clip, I plugged the pedal directly into my interface with no input, no processing of any kind. It's bypassed for about 5 seconds, and I think you can clearly hear where it kicks in. All that said, there's not very much noise at all. In a clean setting, I don't think it's noticeable unless you're playing solo in a very quiet situation. With OD or distortion, everything is multiplied, so it's more noticeable there, but in my mind, it doesn't rise to a level that makes it unusable. I did have a heater running when I recorded, but I tried it afterwards with the heater off and I didn't notice a difference. The heater was off for the very last clip, so that's just pure pedal.
Here's the SoundCloud link to the clips. Zero processing done in Logic - I went into my Mesa Cab Clone directly into the computer (to eliminate any external noise). FYI, I did add the sound of an 8-track tape changing programs between each clip for two reasons - one, I like to highlight when things change, even if it's fairly obvious; and two, it makes me giggle.
Hope this is helpful. And apologies for the sloppy playing.