Was reading reviews, I've never tried the unit. From what I read, the common complaint was that the in-built models are underwhelming. In contrast, I've read far better things about Neural's plugins.
So totally conjecture, but if they do it right, it should be a step up from the existing tones.
I think there are also places where you can purchase good captures, for example the Omega Ampworks folks have released their own captures of their amps. Sounds like a good starting point. I also have no idea, but I'm hoping some of the free captures that have been shared are also a good starting point.
I also have a few amps of my own, so I might try capturing some of those as well.
I won't be selling the bike shop, the Axe FX is a very useful unit to me. I even sold my Kemper after spending some time with it, I vastly preferred the ability to create my own tones, rather than having to be locked into what someone else perceived as a good tone. Great unit, but I struggled with it. I was one of the earlier adopters too, got mine in 2013 and had it for some 8-9 years before I switched.
Portability is one of the main factors that is motivating me to get one of these units. I've busted my back hauling around tonnes of gear and guitars from one jam to another (you could count the number of gigs I've played at on one hand), and I think it would be great to just have a small unit that I could cart around without struggling too much.