Björn Schotte - AJAX: redesign your PHP applications?

"First of all, XMLHttpRequest has a problem: in InternetExplorer, it doesn't work without ActiveX. This makes it pretty useless when being used in companies like HypoVereinsbank or Siemens (both are customers we're working for) where ActiveX has been disabled for security reasons.

Second, the fixed costs for a HTTP requests are changing: while AJAX technology is designed to load just the delta of the data, your application design has to be changed in order to keep the performance: don't include whole framework stuff while you receive a XMLHttpRequest that is only trying to receive three rows out of the database."