What drew me to jQuery over Prototype in particular was the fact you could use css-style selectors to get and operate on several elements at once. This often reduced several lines of code in a loop to a couple chained methods.

Prototype first came out in Feb 2005. Dojo 0.1 was Aug 2005, and 1.0 (first stable, after a total rewrite) was Nov 2007.

I do remember using Prototype with script.aculo.us and thinking it was pretty neat to add some effects to my server-side-created web apps, but that they'd largely stay server side. The first time I saw jQuery, that was when I thought "Yeah, okay, we can actually start building some serious client-side interactions here" instead of just server-generated HTML pages.

jQuery took me from hating (but tolerating) javascript to actually enjoying client-side web development.