So far I'm really liking it. I prefer Simul-Class over Class A. To me it has more of a fullness to the sound than running in Class A. Thought I will say for Class A being only 15 watts it's still loud as all get out.
Pro tip for MKIIIs. Boost R2 for your rhythm tone, and keep the lead channel for leads. IMO boosted R2 for high gain rhythms is different & possibly better than the usual Mark lead channel high gain rhythm sound.