|Great article on Best Practices for Production ASP.NET...|
Important addition to item 4 - if ScriptMode of ScriptManageer is set to "Auto" – then setting deployment retail to "true" would also switch ScriptMode to Release, i.e. release versions of AJAX scripts would be loaded in your page. (I think the main difference is that there is no parameters validation in release version).
The seting is defined in machine.config.