My various web sites, such as prestonhunt.com, Trainster, and Nagbot, have gone through many distinct phases with respect to Javascript:
Phase 1, the original sites: Static content only.
Phase 2, not long after phase 1: Script-generated (usually Perl) static content on my home machine, pushed by cron job to my web host. Still no Javascript.
Phase 3, about five years ago: As little Javascript as possible, but heavy reliance on server-side scripting such as CGI, Perl, and PHP. I used to feel that Javascript support in browsers was too inconsistent to be used effectively. Then Google Mail and Google Maps came along and showed everybody how things should be done.
Phase 4, about two years ago: Not wanting to become locked in to a particular toolset, I eschewed Javascript frameworks like Prototype. I coded all Javascript myself. This was often a laborious task given the lack of good debugging tools and also the infuriating inconsistencies between browsers (of which IE6 is far and away the worst offender).
Phase 5, about one year ago: Finally bit the bullet and adopted the Prototype framework. Life got a lot easier, but Prototype itself doesn't do all of the Ajaxy things that I like to do (like auto-complete-as-you-type, light boxes, fade effects, and so on). So I started layering different libraries, including Scriptaculous and MooTools.
Phase 6, about two months ago: I've found religion, and its name is JQuery. JQuery's elegance is so beautiful that it almost makes me want to cry. The documentation is outstanding. And it encourages community support through plugins, which quickly become indispensable -- stuff like auto completion, rounded corners, table sorters, tooltips, calendars, etc. And because the plugins are all based on the common JQuery foundation, they usually play nicely with each other. I'll be posting soon about how JQuery has made life much easier for me. In the meantime, I'm busily migrating all of my sites to it.
Related links: Why JQuery's Philosophy is Better, JQuery - Javascript that doesn't suck!