For the prototype.js users -- is it worth it?
patio11: We use it at both the day job and in my business.  It is clearly better than nothing.  If I were starting from zero today, I'd take a very close look at JQuery, as I think the web development community is rapidly standardizing on JQuery, which means pre-made things that I want to incorporate are disproportionately written in JQuery.  However, I have never been totally unable to find a Prototype moral equivalent for the types of controls I have wanted.  (e.g. a color picker)Your mileage may vary, by the way, but I think it cuts about 90% of the pain out of AJAX development... leaving 90% to go.