I have been unsuccessful in getting it to work with AJAX thus far... so if anyone out there has gotten it to work, please let me know what you did because I would love to know how to get it to work.
Ok... the recording part isn't where my issue is... it records everything fine... but when I replay it, it fails... I have found though that if I disable everything but the last request that contains all the data for a form for example, that I can get it to work that way...
I have recently tested a Ajax application and i had a similar problem in executing the script. when the script was recorded it did not have any automatic correlations made as the data was transferred in XML format and not in HTML tree. I think RPT is not capable enough to correlate such data. I had to manually correlate multiple values used in subsequent requests and then the scripts worked fine. Try to do this, it might help you.
I have been able to test ajax application with RPT however. You need to break out any ajax parts into their own page, so that they can be sent sequentially, since RPT groups things on a logical page. Doing that will allow you to test AJAX fairly well.