I think someone mentioned that there should be somewhere to write reviews / leave feedback for the ReRack Extensions - this is a great idea.
Anyway, this compressor is the second unit I've purchased from FXpansion (the first was EtchRed) and I'm very impressed yet again. The audio just seems to come out sounding smoother, tighter and just nicer without too much tweaking. For €25 it's a complete bargain. In my opinion it's more transparent than the built in SSL channel compressors, but I have only used it at low to medium levels. I'm looking forward to trying the channel version just to see if there's much difference...
If you want a change from the MClass and Comp01, try this baby out... I don't think you'll be disappointed.
Just in case it's of any use to anyone, this unit is great on single channels too, not just busses. So far I've used it on bass and synths. I still prefer Comp01 on percussion though but that's because I prefer them to be un-subtle.