For the prototype.js users -- is it worth it?
bkrausz: We use both jQuery and Prototype together in our app.  I love jQuery and would love to use it exclusively, but our architecture was build around Prototype's class extension capabilities, which I have to say are pretty damn convenient.  Beyond the ability to make JS much more easily handle inheritance, I haven't found much benefit from it over jQuery.I'm also specifically annoyed at how it tries to modify the HTMLElement prototype, since that's not allowed in IE < 8, and caused some weird bugs for me (sure, it should be mutable everywhere, but let's be realistic: IE < 8 has a huge market share, and should have code consistency.  After all, that's what JS frameworks are for, amongst other things).