IMHO,
If you have seen only 2 applications of Ajax then you need to look further and also realize that all that YOU see is not the actual/entire/complete universe.
We normally see applications that we come across, the Ajax applications I use everyday are GMail, Google Maps, Google Talk, I don�t know how many other google apps have been developed using Ajax.
Using Google Mail vis a vis Yahoo Mail itself demonstrates the benefits of using Ajax, and Google Talk is an amazing example as well.
Yahoo News uses ajax as well, just click on any of the links within a news article, these are some of the things that I have come across which came to my mind right now, I am sure there are many more (out there in the entire Universe

).
This technology has just entered the market and people are still debating how/why/if/should/when to implement and incorporate it into there apps.
The real applications of this technology will not be visible on the web so much as in Enterprise applications, used within organizations, these will start appearing slowly as development time for such applications is longer. Enterprise applications that currently use Active X or Swing/Applets on the client side are good candidates for switch over to Ajax (info on why/how/if for this is available elsewhere on this board)
Everybody can implement Ajax in a small way right away for a couple of pages or processes, example, display search results on the same page after making a Ajax request. These things are easy to do, the real challenge and power of Ajax can only be unleashed by using them on an application level, which requires reworking the architecture of the project, projects which are already under development might not be able to do this switch but the new projects being designed by smart System Architects and designers will definitely see Ajax playing a big role. I foresee these 'smart' project managers will definitely learn what they need to know, patterns in particular, from Chris's book (Ajax patterns and Best Practices : Christian Gross)
[ February 23, 2006: Message edited by: Liyaquat Ali ]
[ February 23, 2006: Message edited by: Liyaquat Ali ]