An anticlimactic conclusion about the ASP.NET AJAX Framework - this framework's niche seems to be the internal (intranet) business application realm that depend on ASP.NET Web-Forms. These applications have a handful of users, a couple developers, no performance or bandwidth requirements, little ambition for future growth, and the developers typically embrace dragging & dropping controls in Visual Studio. In this case the ASP.NET AJAX Framework provides some eye candy, and patches the broken Web-Form metaphor by cramming AJAX into the ASP.NET model, but then comes along the ASP.NET MVC Framework, Silverlight, WPF and ... ??? Goodbye ASP.NET AJAX!

Interesting observations:

How many applications explicitly state that they use the ASP.NET AJAX Framework?

• 25, this includes sites like DotNetNuke (with a reputation of being slow), view the list here.

How many of these applications are relatively high-traffic?

• None. ZERO!

How many applications explicitly state that they use the YUI AJAX Library?

• 89, view the list here and here.
  

How many of these applications are relatively high-traffic?

• Quite a few. A couple notable sites: Flickr, Slashdot, Linkedin, Paypal, O'Reilly, My Opera.

How many applications explicitly state that they use the jQuery AJAX Library?

• 516, view the list here.
  

How many of these applications are relatively high-traffic?

• Many. A couple notable sites: Twitter, Digg, Dell, Slashdot, BBC, Netflix, Technorati, New York Post.

If no high-traffic application uses the ASP.NET AJAX Framework then why would you? Actions (or lack of action) often speak louder than words, and it appears that the ASP.NET AJAX Framework is not suitable for the real world.