Fantastic great fun...for about 45 minutes...
The Bad: ...for less than an hour; premium $35 price (now that it's cancelled, it's way more); no way to save creations; absolutely no depth.
Electroplankton is one of the most interesting uses of the DS features ever. It basically involves ten different kinds of "plankton" that make sounds in different ways, and you just mess around with them. There's really no core game here, no objectives or unlockables, nothing but pure straight up novelty. And that makes the game worth absolutely nothing as a purchase.
As a tech demo, Electroplankton really shows off stuff that could be done with the DS. There's very interesting uses of the microphone, the touch screen, and the general layout of the DS that are tons of fun to mess around with. There's a plankton that records and remixes sounds and your voice, there's one that moves in patterns and makes piano-like noises, there's one that shoots out of the water and makes noise as it hits leaves...and quite a few more interesting ones. It's amazing to play around with the game, especially with headphones, but again there's absolutely no lasting value to the game as the thrills end in less than an hour of play.
It doesn't help that you can't save any of your musical creations either. If this was a minigame in, say, WarioWare or something, it'd be great. But on it's own as a premium-priced DS game? That's not excusable. It isn't even worth five dollars. More depth and options would have helped immensely.