Late to the party, and inconsistently "on topic".
I loaded up Beta 12 this evening, and did a full reset on my "go to" presets. JCM800, Princeton, Deluxe Reverb, Twin Reverb, JTM45, Plexi 50 6CA7, 1970 1959 Super Lead and JC120. I am unusual in that my main tube amps for the last 25 years have been Marshall 2203 JMP 100W Master Volume Marshalls (which are very similar to the "JCM800" models in the Axe FXs), but I have tended to run with the gain pretty low (3 -4), the master as high as I dare (much past 4 is deafening), and my #1 amp is modified for reduced gain and more bass in the preamp section.
I was suffering a little from "listener fatigue" by the end of it, so the classic 60's and 70's Marshalls will need a little more work, but this is definitely best so far, and by a country mile, for modelling algorithms. JCM800s have lost the weird high-mid fuzziness I used to find myself trying to dial out. Tone controls in authentic mode are authentically ineffective as per real Marshalls. Oh, and the Roland JC120 is fully fixed to behave like a JC120 as I can best remember playing through one!
I will probably start from scratch on all of my presets either now, or when the public release version becomes available. Have to agree with all that have said so, that this is a major change in the "feel" of the models, and it is probably not that obvious from youtube videos. Ignoring "chug", the spit, snarl and response in general feel more amp-like. With the Fender models I use, there's a delicacy, smoothness in response, and general good attitude (OK, maybe not from the Deluxe Reverb, that one is a Marshall in Fender clothing in real life as well as in the Fractal'verse, total hooligan's amp, I love it!) that was never apparent to me before. There is a little more work to do before I am happy with my main presets, but for me, definitely worth resetting all the amp blocks entirely, happy in the knowledge it's going to sound and feel remarkably better in any model, and that any work I put in will be a tiny fraction of that done by Cliff and team.
Thank you Fractal Audio. Cygnus is awesome in ways I hadn't dreamt of.
Liam