I have.
I have been fermenting under pressure for several years.
I will start fermentation in the low 60's and at ~10psi or so, after two or three days start raising the pressure and temperature to insure it finishes and to carbonate the beer. I will let it get to 30-35psi, occasionally higher, keep it there for several days, then drop it close to freezing for 3-4 days, most of the CO2 will go into solution, and the fermenter will often times be at 8psi of so. I then transfer under high pressure the the serving kegs using the spunding valve to control flow rate via pressure. The high pressure transfer minimizes foaming and gets the job done faster. I would typically brew 10 gallon batches and have two kegs jumpered together and sometimes a third to control the flow rate to act as a buffer so to speak, sometimes the batch would be a bit over ten gallons and the third keg would catch the excess. I would put it online and it would usually be gone quickly. It does waste a bit of CO2 doing high pressure transfers, but so what, CO2 is cheap enough, as to not to worry about it.
I was fermenting in sanke kegs, I now have a kegmenter, but haven't had time to use it with the new job role that I currently have (gone 9 weeks and home for 4 weeks, then do it again). I'll most likely get a second kegmenter when I actually have time to brew again.
I'll most likely sell of a bunch of the equipment that I have collected for the sanke kegs, transfer rigs, ball lock triclover fittings, the seals, clamps and whatever else that I'm not using and don't feel like I will use moving forward.