Have had my Kemper for a few weeks now, and - like most people - have been blown away by how realistic it sounds/feels.
However I was initially a bit underwhelmed by the onboard Dist pedal effects... that is until I started experimenting with the Boosters. With the Dist pedals I'd just been leaving their volume setting at 0, however with the Boosters you obviously need to use the volume setting to get the boost... - and I found that even using just the "Pure Boost" I was achieving nicer lead sounds than I'd previously got from the Dist pedals.
I then went back to a Green Scream preset I'd saved, and set the volume to where I'd had it on the boosters - instantly got the same fat/smooth/fiery lead sound I'd liked from the Boosters, but now with some extra Green Scream overdrive as well (though I ended up turning down the gain on the pedal a fair bit from where I'd had it before to get the best tone).
Experimenting with the other Dist pedals, I found that if I first set volume (with drive at zero), then added drive to taste, was getting much better results than before - in fact they now all sound fantastic!