For the Geocities comparison commenters... My takeaway was not "Here are animated icons, you should litter all your pages with them" but rather "Here are animated icons, if you have a use case for them, then these are a very good option".
For the too-much-animation commenters... Are you actually surprised that the demo page stuffs a lot of icons into a page in order to demonstrate the range of capabilities? See above -- the intent is that designers should use them sparingly and appropriately. Is animation necessary? Probably not. Can it be engaging if the execution is good? Without a doubt.
These are very nice-looking icons that appear to offer quite a bit of flexibility. I think that they will seem more natural in contexts where lightweight animations (drop shadows, spinners, etc.) are already used: alerting a user to an available interactive element, on hover as a user prepares to perform an action, during a wait period while processing occurs, or drawing attention to a completed action.
Many of these are pretty subtle or clever animations. If you can get past the notion that "no one in the world can use animated icons well", you might realize that these could be used in moderation to add a hint of whimsy to a site.