I haven't had much time to play with it yet (John only released it last night), but it's been interesting to compare it with my own SVG based implementation. SVG, being DOM-based, seems to have a ceiling for the number of objects that can be included in an animation- once that ceiling is exceeded performance begins to suffer noticeably. John's Canvas-based version seems to handle much more complex animations without pinning the meter. There are also a couple of features in John's library that take advantage of the new Canvas functionality in Firefox 3. I'm really looking forward to spending more time playing it. Great work John!
You can download the latest Lily beta here - it includes the "processing" external.