When I first uploaded 18.03, I felt as though all of my usual amps felt less "smooth", less "liquid"... I played around with it quite a bit, and updated to 18.04. What I found was that the sound I was looking for was still there, it just wasn't where I left it. (Because I'm an idiot) I started turning knobs that didn't need to be turned... instead of just playing on the amp a little while. The more I played around, the less I felt the need to turn knobs. The settings I used to use in 17.04 were unnecessary, and just didn't work for me with the new firmware. Though, I do find myself cutting a little more bass out of the mix.
On a side note, the new preamp tube settings are cool. I noticed a slight difference between all three settings; I will need some time to work through my patches with each one. My main go-to lead patch (Das Metal) is adjusted to the "test" setting... I'm going to stick with that a while and see how it feels in the overall mix next practice.