Can we leave the toolkit evangelism to a different thread? The subject is behavior which was routinely implemented better in the mid-90s without using JavaScript at all.
(That said, I'm certainly not saying that JavaScript doesn't allow much richer UIs, only that as an industry we're often prone to assuming that the cooler tech automatically implies benefits to users – e.g. ask anyone who's had to reload a simple form UI because the AJAX logic failed to handle network / server errors, out of order dispatch, etc. in a non-confusing manner – or everyone should love your favorite tool without asking whether it has actual benefits for what they need to do.)