I bought the M2 Optical Compressor about 2 months ago. It really is as good as Yanek says it is. If you go to the Miura website, there is a page on the M2 under Products>Pedal. It's made really well, is dead quiet, and is super easy to use. The sound is very similar to a classic optical compressor, i.e. very smooth but slow to release, as apposed to VCAs like a dbx that lightning-fast but aggressive and 'sterile' sounding.
If you are looking for nice, smooth, barely noticeable compression, like Yanek uses in an 'always on in the signal chain' way, the M2 is really tough to beat even with rack-mount units. If you want a hard peak-limiter, this is not the pedal for you IMHO. In that case, go for a VCA-based comp/limiter like the Keeley Bassist (my choice) or the Maxon CP9 Pro+.
Good luck!