Are there Usability Issues with AJAX?

The nature of updating a page dynamically using data retrieved via AJAX interactions and DHTML may result in drastically changing the appearance and state of a page.
Since the pages get updated dynamically, the state of a page may not remain the same.
So the behavior of a page may need to be defined in each of the following user actions:

• Navigation using the back or forward buttons of the browser
• Book-marking a page
• Sharing a URL
• Printing a page at any given time

Navigation:
The output of the user actions like a page refresh, forward or back navigation, etc need to be defined.
In this case using a JavaScript framework such as Dojo that provides API's history manipulation and navigation control would be simpler.
Book-marking and URL sharing:
Dojo provides client-side interface for book-marking and URL manipulation.
Printing:
Issues could arise while printing dynamically rendered pages.
Source