I bought a KSL tab a few months ago. So far I've only used it a few times. The thing is so bulky that I can't even pull an arrow out of my quiver without dropping it half the time.
From what I can tell, the palm plate is sort of a "negative reinforcement"; digging into your palm causing pain if you don't hold your hand just so.
As far as finger placement, it's no more precise than a Cavalier or AAE tab with a simple backing plate.
In fact, the metal plate interferes with the arrow nock, giving me an annoying "click" as the plate flicks against the end of the nock. Just distracting enough to make me wonder when the arrow will remove itself completely from the string and fall to the ground giving me the dreaded "dry fire." The AAE is shaped in such a way that it's not an issue. I was disappointed to learn that such an expensive tab as the KSL would do this.
All you really need is a reference line that you can easily repeat, which is what the backing plate is meant to do. Stitched leather tabs like the Wilson is just as good in this regard.
I won't shoot with again until I have the time to disassemble it and take a file or grinder to it to fix the problems. One of these days I'll give it a second chance. At that price, I really don't have much of a choice but to try and make it work.