AJAX is growing very fast and that is the reason that it contains many issues with it. We hope with the passes of time, they will be resolved and AJAX will become ideal for web applications. We are listing down a few issues that AJAX currently suffers from.
Complexity is increased
Server-side developers will need to understand that presentation logic will be required in the HTML client pages as well as in the server-side logic.
AJAX-based applications can be difficult to debug, test, and maintain
Toolkits/Frameworks are not mature yet
No standardization of the XMLHttpRequest yet
No support of XMLHttpRequest in old browsers