I had my first run with Kemper in 2012. I couldn't stand the aliasing, which at the time was quite severe for my tolerance level.
I eventually got back to Kemper when they improved aliasing performance. I'm surprised they (apparently?) act like aliasing was never a problem for people.
Profiling for me was always a mixed bag. Profiling multiple distorting stages (like preamp and power amp gain) often resulted to an exaggerated cocked wah sound. But the manual itself explained results may be off with such chains.
In cases when profiling worked its best (hundreds of profiles made, many amps), at least with distorted tones, there was a"tubescreamer"-like feel and sound.
This is easier for me to feel than to hear, but there's many blinds tests I've made where it's audible enough. Depends on many things, including what you play, in my experience. Especially the feel is something I grew to dislike.
Saying all this, I used to make public tests and hoped Kemper would improve profiling. It was so close yet somehow so far. Eventually, after enough (arguably) gaslighting from the Kemper side, and the feeling they believed accuracy to be perfect, I stopped caring about the matter and moved on.
I don't think Kemper is a bad unit. It was great when it came out and you can still make great albums with it.
That said, I do hope the MKII profiling is better. I'm glad they finally seem to have understood or accepted that profiling is not perfect and are taking steps to improve it. Would have been nice if some of us old users got a cake in the mail or something, but it ain't about to happen!
I won't buy a Kemper unit again, because not in the market for anything, but I hope the new unit does what marketing seems to claim.