Atlas has many options to go for development you can choose to use all the server controls and extenders which provide very limited AJAX functionality (even with no AJAX functionality sometimes just javascript & CSS llike modal popup ) , this model sounds more like what the Atlas project promissed

   Or you can go for the XML Script style which is relied on the Javascript programming it's flexible it just drives you back to the problamatic hard to debug and edit model , also without a good UI designer it's pretty time consuming and very hard to debug, also you will lose the functionality of the extenders which are not compatible with this model