Well, I have put my FCS P3SL into use. It's a prototype I bought from Roger. All variable controls, no feedback mode, simpler meter and only A/R and RMS modes. No transformers either, didn't want any.
I have had it for over a year, but I simply had no rack space in the old place to put it in for comfortable reach.
I'll just repeat after what other people say: It is a really, really good compressor and is likely my new work horse. The RMS mode gets my love, but I just used the A/R modes in a black metal record with success.
As it's all continuously variable, I'm thinking of putting in some stepped attenuators. I was going to do them all, but I actually sort of like the variable controls. So it might be I'll just go for the gain, stepped. No L/R balance to worry about anyway. But ask me again after I've tried to recall it.
I put it after my Knif Pure Mu compressor. I've been missing some clean gain after it.
Also, I know the output of Roger's compressors should be a killer in driving a transformer, but to my surprise, the current feedback op-amp at the output of my BPEQ is much better at driving the input of my Knif (which is non-standard to the other Pure Mu's - 2k5 L-pad attenuator and an unbalanced input).
Anyhow, the P3S must be even better than my prototype. Everyone should get one.