Lot's of free compressors these days. Every single one of them has it's own trick. Point is, that in most cases, those payware ones will be always a bit better, more analog. Big companies have resources for real hw units, possibility to meature them. Not much of freeware developers can do that, so they read about behaviour and then mimic it in some way that kinda works, but it's not that precise most of the time.
Is there way out of it? Yes. F*ck them all, make it simple, but solid! Exactly what jsCompShaper does. It features internal sidechain EQ, paralel functionality, ability to continuously switch between compression and waveshaping and last but not least, crazy oversampling.
All you need really is throw it on drum buss and play with settings to hear the sound. In some settings I swear it reminds me of SSL sound. (Didn't even touch real console, so can't tell "for real", but from internetzz.) It doesn't have HP filter though, so it's better for drums where you don't want kick completely low-endish.
That shaping is interesting. Some cool character can be achieved, but especially on the drum buss it does just a little changes, even smaller when used in paralel.
Another thing is versatility. I didn't work with voices that much lately, but i believe it's great on vocals. That EQ and some special voclal presets suggest it. Or knee for example. On some compressors you turn that knob and almost nothing happens soundwise. Not here at all. Hard or soft as you like.
What I love the most is the oversampling. I believe it's one of the things that define sound of those big payware plugins. It makes it haeavy on CPU in jsCompShaper, but result just sounds good. Defined. Smooth. I guess not much far from simplier Waves plugs.
Conclusion: I guess old HW companies have spent ages and milions to make their compressors behave as ideal as possible. SW companies just as much to make it behave as not-ideal as possible to get close to products what HW companies made. As a result there is so much of different coloration in the world that no ordinary listener can really tell. That means on budget, only thing we should be really concerned about is, whether it sounds good or not in general. ...and this compressor definitely does. It won't sound exactly as any HW particularly, but really good anyway! :) I don't mean that emulations are meaningless. I just mean (and hope) nothing to worry about using plug like this. :)
What I love about free plugins is that there is not much of decription needed now, just go and try it for yourself. :) For me, this is discovery of the year so far. Love it!