The new version 6.6.13.2 will support Pocket PC 2003 and Windows Mobile 5 devices including Smart Phones, too.
I'm running my web site http://www.ajaxpro.info/ from my mobile phone using GSM (slow speed) and GPRS. It is very nice to see that the page is showing the message "Your browser is working with Ajax.NET Professional!!" in top of the page. I will show this message in my callback function that will save the browsers user agent in the log files you can view at http://www.ajaxpro.info/log/ (not live, updated from time to time). Notice: I have only modified all the DHTML stuff on the default.aspx, other web pages may not work. Hopefully I have some time during the next days to update some of them, too.