I'm not really sure how to answer this. I've had the II from FW 1 and I've been able to get the tones I want out of every firmware when I needed them.
I think it's all about the FEEL for me in this one, which to me is now pretty much indistinguishable from my army of amps. The Axe has always been capable tonally if you put the work in, and there have of course been many great changes that make this easier every FW, but the Feel has never been like this. Amazing.
With the exception of a little 3 watt, super clean tube amp I built myself to use as a pedal testing platform, I haven't fired up a "real" amp in the studio in quite a while.
I don't use the Axe live, always used my amps and pedals (not because of any shortcoming of the Axe, just a personal thing) but now, I don't think I can ignore it anymore. I think one of my units is going to become my live rig, by not using it, I'd be missing out and I was never totally convinced of that live before. I always thought what I used was enough.