I started peeling off the old grips, but that became futile after they were about a third of the way off. Then it occurred to me that even if they came off intact, they were likely too stretched to be useable again... time for the razor blade.
The throttle side split easily and came off with minimal coaxing. The left grip was an entirely different matter. It seems Kawasaki determined that the left grip is the one part of the bike that won't ever break loose due to vibration, impact, or Act of God. Even after slitting the length of the stock grip it refused to yield.
Adding Goo-Gone to the mix created a near disaster, melting the stock grip and making it impossible to remove in one piece. I ended up shaving the entire thing off with a razor blade, then using sandpaper to remove the last of the glue and rubber. NOT a good solution.
<-- pic showing the heinous mess after Goo-Gone and a shave.
Once I had the left grip properly cleaned (and a bit scarred from the sandpaper) the new grips were ready to go on.