There is a way that one can employ Ajax while preserving functionality for users without javascript enabled, search engines for example. I've written a 2 part series on my site about this at
TeraTask Technologies, LLC - see "Search Engine Friendly Ajax Websites" and "SEO Friendly Web 2.0 Sites - Part 2" for details.
The only "new" thing with Ajax is the ability to call back to the server using Javascript without having to load a whole new page. There were ways around this before (frames, for example), but now it is easier than ever and supported by most of the major and minor browsers which have support for javascript. As with all technologies, improper applications are to be found everywhere (take Flash designers for a great example). Ajax does have a very important place in the future; it would have been nice for it to have been properly named however so as not to attempt to usurp Javascript.