There's been an inordinate amount of buzz about AJAX in the last few months. Everybody's looking to do something with it. There have been a few people who
genuinely don't seem to care for it consider it a potential liability due to its intricacies, but today is the first time I read a post that I agreed with 100%. Marcus Baker of SimpleTest made some observations. In his post he argues that most of the uses are actually going against learned behavior. To boil his case down, he's pointing out that AJAX is great in environments where you're striking out in new territory or where you're trying to mock existing behavior (moving from a desktop app to a web app for example), but to use AJAX for the sake of using AJAX defeats its usefulness.
The post is definitely worth the read if you're interested in AJAX and how it can be used.