I've used the Kemper for 8 years or so, and still marvel at how great it is every time I turn it on. Just had an intense shootout with a Fractal FM3, and as wonderful as the FM3 is, it lost to the Kemper as the Kemper is simply more musical. It has captured my heart.
All that being said, Liquid Profiling has really bent my mind on the Kemper, in most cases it has greatly addressed one complaint I had with the Kemper; the inability to accurately tweak an amp profile by using gain and EQ. There have been many cases where I could not find a particular tone I wanted out of a profile pack due to EQ settings, but Liquid Profiling has given a clean solution. In every case I have tried (only retrofitting standard profiles with Liquid), it has only made significant improvements in the models. Each model I tried I ended up saving as the improvements were so stark. And they were great to begin with.
Another improvement was to the harmonic accuracy of overdrive and distortion in a profile. I never did feel that Kempers quite got overdriven Fenders right; being the owner of an original 5F6A tweed Bassman, I'm very familiar with the tones. But I took a Tone Junkie profile of a tweed Bassman and Liquidized it; boom, there it was. Stunning. Having that proper tone circuitry in the middle of the amp topology is a BIG deal in harmonic generation.
I have always not been fond of the effect the Kemper has on a profile as the previous profiles "assumed" a gain structure from noon on the Gain knob on up. This made the overdrive texture of the amps sound more Marshally to me with the gain above 5. The Liquid profiling appears to keep the gain range of the profile within its limits to the actual amp, and I much prefer this. All the EQ and gain settings then are accurate to the actual amp design, and higher gain isn't estimated.
The only down side with Liquid Profiling is we now need to do what modeler users are so familiar with; beg and plead for a particular model of an amp that doesn't exist. I'm eagerly waiting for a Dumble ODS Liquid setting, as well as a Heritage G12-65 imprint. But I'm not complaining at all.