I was not impressed. On the client side I would use it for very few things and when I tried the server side version I decided that I would rather stick with Perl and CGI. Although I did not like Perl, I could get things done with it. (Oh, I just remember: also Cold Fusion!)
My opinion of Javascript has not improved over the years. I worked with Javascript for a while and in complex enough problems that my name ended up on 2-3 patents and patent applications. I no longer work on the web, but I have occasional need for Javascript and I always hate my time with it.
This will be an unpopular opinion, but frankly I am perplexed by its popularity, because it is neither simple nor elegant.