I thought the episode was decent. I laughed for some of the time, but not during the whole thing. I liked how the plot was about Plankton, but it didn't involve him stealing the formula. In fact, I don't think SB and Mr. Krabs even knew that Plankton was behind the whole plan in the first place. Finally, the ending solved SB and Mr. Krabs' problem, so it was all good. In short, this was an OK episode that was a nice change of pace as far as Plankton-themed episodes go.
Final score: 6/10.
EDIT: As a whole, all the new episodes that aired this week were pretty good and I can't wait for next week's! :)