What sets Ajaxium apart from other possible solutions?

Put briefly, Ajaxium is not simply a callback control or a placeholder that enables AJAX for just a few controls contained therein. Ajaxium captures and processes the entire output of all pages for which it is enabled, and offers a lot of unique features:

Ajaxium enables AJAX for ASP.NET controls even without using any additional panels or controls placed on the ASP.NET form.
Ajaxium supports all browsers which lack required features owing to a graceful automatic degradation to the classic ASP.NET mode. Thus, Ajaxium-powered sites work even when JavaScript is disabled or the browser doesn't support the XmlHttpRequest object.
Ajaxium-powered sites are indexed by all search engines. This is achieved by a graceful degradation to the classic ASP.NET mode performed automatically for all remote clients who have no JavaScript support. Since search engines ignore all JavaScript code, they do not see Ajaxium at all. Being invisible and leaving HTML source untouched, Ajaxium helps search engines to index the website.
There is no need for developers to define explicitly which panels must be updated even for optimization purposes. Ajaxium automatically detects changed regions and performs an optimal update of single panels, multiply panels or the whole ASP.NET form. Ajaxium even automatically rewrites the entire document content if changes occur outside the form and document body (for example, in the document header).
Even if additional panels are used to reduce page flickering in old browsers, Ajaxium always analyzes the whole content of the web page. If updates must be applied outside all defined panels, Ajaxium applies them for the ASP.NET main form or rewrites the entire document.
Ajaxium supports transition from one ASP.NET page to another.
Ajaxium allows you to use traditional ASP.NET postbacks with AJAX in any combinations.
If a server-side error occurs or if the server returns an unexpected response (for example, a default error page), Ajaxium replaces the current document with a returned response, making the response accessible to the visitor.
Ajaxium supports all ASP.NET server-side features and technologies, including data binding, session states, authorization, etc.
Ajaxium supports ASP.NET cookieless sessions. As a result, applications that do not use cookies can be just as well AJAX-enabled.
Ajaxium is capable to revert to a traditional ASP.NET - both at run-time and during each separate session.
While storing required information in the session state, Ajaxium gracefully handles session timeouts and all related pitfalls.

To date, Ajaxium enables AJAX on Internet Explorer 5 and above, Mozilla FireFox 1 and above (as well as other browsers which use Gecko engine), Opera 8.50, Konqueror 3+ and Safari 1.2+ (as well as other KHTML-based browsers). All other browsers view Ajaxium-powered websites as classic ASP.NET websites. Even if your favorite browser is Lynx you can access any page at an Ajaxium-powered site.
With such features in hand, this powerful solution puts us into a dominant market-leading position in the field of AJAX technology.