I've had the last month or so to live with this beast. I've been mixing a rock record through it and I have to say this thing is absolutely INCREDIBLE.
The Carnhills definitely add major league heft to anything through it. They are switchable, but I think it would be silly to switch them out! I've got a Folcrom summing box so my mix signal chain is GR MP500 2NV > API 550 B > FCS P3S -- Everything comes out f'ing ENORMOUS. I keep the HPF engaged and usually keep my ratio at 1.3:1 and kiss it for 1 to 2db of reduction. It's been in RMS mode and lately I've kept it in Non Linear mode. I also dial 2db back at 30 on the API's and this seems to help keep all that xformer iron between all my pieces in check.
It's an impressive piece of gear at an extraordinary price.
Speaking of electronic music...that's what I make. Here's one of the first things I mixed through it. A little glue to tie the room together:
SENTRALL - Rollmottle - The Yearsong (Final Mix) - SoundCloud