Before you do that...

@blaix, @thomasw, do you have any opinions on switching to CSS transitions?  IE9 would not see the animations if we do that, but everything would otherwise work. There are [polyfills for this](http://www.useragentman.com/blog/csssandpaper-a-css3-javascript-library/), but I've never bothered with them. (IE9 users deserve their sub-par web experience.)