I had a hh2, now on the runner. It's great, there isn't much about the hh2 I miss. It takes some getting used to descending, its not exactly like releasing a hitch. It goes up the rope and tends amazingly well. Sometimes too well, you have to throw a slip knot in above sometimes or it will gobble slack. The other thing I miss about the hh2 is how bombproof it is, the runner seems fragile in comparison.
Never tried kernmaster but you should be able to adjust it to play nicely. It doesn't take much adjustment to completely change how it functions so adjust in very small increments, like 1mm at a time. I would start with the bollard wide open and go from there. I also feel like there is a slight break in period so once you are comfortable with it, bomb out a few times and get some wear going. This is all subjective but it has worked for me and two other climbers I work(ed) with.