Also, consider is how easy it is to do your "Slide from bottom" effect with CSS.
http://jsfiddle.net/S7ZuK/3/ Is it really something you need a whole plugin for? I don't use any basic Fx classes anymore unless I'm sure they completely and predictably insert new DOM fragments (and delete my old ones) instead of trying to worm into my markup "harmlessly"... tend to use CSS transitions, w/Moo as the glue between events and toggling CSS classes. And when something like a Tween is necessary (when IE is deemed a "first-class" Fx client), you can see here you'd only need to animate one property (height). Trying to keep the transitioned elements to a minimum, and the markup and CSS tight, helps you write a simpler Tween/Morph helper. But this is just me. I can understand why people like a bunch of prefab Fx. . And I don't always try to rewrite really cool Fx myself; I might well rebuild my markup around the quirks. Depends. -- S.