Bearing in mind that all browsers (in common use) that support border-radius and gradients, also support SVG and canvas, and that SVG and canvas let you do more, are generally more performant, and have fallbacks (SVG particularly) in older browsers, why would you use Donatello?
This looks cool, you might be able to use move.js for the animations:<p><a href="http://visionmedia.github.com/move.js/" rel="nofollow">http://visionmedia.github.com/move.js/</a>
This whole ninja turtles thing is going to get out of hand. I already know of at least one other Donatello library based on Raphael.js which does something different.<p><a href="https://github.com/postmodern/donatello" rel="nofollow">https://github.com/postmodern/donatello</a><p>You couldn't have picked a different ninja turtle?