Some were surprisingly good (the ones with green chocolate), some were merely surprising (apple, raspberry), but most were surprisingly bad (butter, pumpkin). There was one I really liked, but I have no idea what it was; if they ever sell it in the UK, though, I'd go for it over a regular Kit Kat.
As for the worst one, well none of us could tell what it was supposed to be, but it tasted of fish. Fish and chocolate is not a good mix.