Eileen,
Here's my take on it: When it works, Javascript CAN be useful, efficient, and time-saving. The problem that I have with it is when webmasters create sites or portions of a site that RELY on Javascript. To me, that's just laziness on their part... and it's inconsiderate to users who don't have/don't want Javascript.
When a user without a javascript capable browser (there's more of them out there then you probably think) comes along, the site (or individual page) is virtually useless. It can be extremely frustrating.
Not only do you have to consider those browsers that can't handle Javascript, you also have to take into consideration users who voluntarily turn Javascript off (I've been known to do that myself-- I ALWAYS have Java off, and some days I'll turn javascript off as well).
I've been working as a webmaster for quite some time now, and I always try to design the pages I create to work flawlessly on ANY browser (I'm a big supporter of the "Any Browser" campaign BTW-
http://www.anybrowser.org/campaign/). My sites may look better on some browsers than others... but they'll ALWAYS work.
Things like Javascript, Java, frames, extensive graphics, etc, should be EXTRAS in my opinion. They should be used to ENHANCE a page, and *never* be a requirement.