Has anyone used http://flashblocks.com/?

Any experiences, positive or negative?

Any limitations, such as :
You must use certain components, or
You can't use certain code, or
You can't perform certain animations/functionalities, or
You must strictly adhere to a set of guidelines laid out by FlashBlocks...?

Any info would be helpful, including if you know of a better alternative to FlashBlocks.

Thanks.