In all honesty i think that >B is great as spacing tool, and of couse it can rack up the damage nicely too, but to be honest i dont use it for KOs, i actually just keep using it a lot to keep the threat on all the time, and just to keep spacing, spacing, and spacing some more. If you land a down smash at killing percentages, i would almost always recommend turning around and baring "Ikki style" (hehe im sure hes not the only one that does it but i was impressed by his videos).
In my matches i save up almost always my bair and not care about damage decay with my >B, since >B is there for spacing and for keeping your opponents honest mainly, of course u can rack up some nice damage with it, but i think that for KOing your better off with a saved up bair.
By the way, i dont have my Wii right now so i cant check, now that we speak about punishing, can someone test how fast she can pull off Spot dodge > downsmash? Kann it be something as messed up as ROBs or our spot dodge downsmash comes out too slow to punish anything?
Thanks