I just created a new release and uploaded it to CodePlex.

The feature improvements are for now

• Fixed some issues with the control hierarchie
• ScriptManager gets initialized with all properties from the parent page
• More Controls from AJAXControlToolkit work, yes even the ModalPopupExtender!

You can find an updated version of the PartialUpdatePanel ASP.NET-Control here: PartialUpdatePanel 1.7.

So what is the PartialUpdatePanel?
The PartialUpdatePanel provides real partial rendering of ASP.NET pages.
By using this control you can experience performance improvements compared to ASP.NET AJAX UpdatePanel, because not all page data needs to be transferred. Only a minimal set of data is being transported between the client and the server before your UserControl is made fully functionable.

Usage scenarios
Exemplary scenarios for the usage of the PartialUpdatePanel are:

• Autonomous sections of your page that require PostBack-support but not the environment information of the entire web page (e.g. data lists with paging support where the user can browse through news, feeds, mails, etc.)
• User feedback when your control has to complete long operations. In this case use a PartialUpdatePanel with render method “Clientside”. The surrounding page will be displayed with a waiting message. The user will receive an adequate feedback that something is going on and he needs to wait until it is done.

More information and a version history can be found here: http://www.codeplex.com/PartialUpdatePanel.

On codeproject I wrote an indepth technical article how the PartialUpdatePanel works: http://www.codeproject.com/KB/ajax/PartialUpdatePanel.aspx