I was working on migrating the Petshop example when I came across a problem. I had put the header control in the master page and needed to access the properties of user control in one of the content pages.
The master page itself derives from UserControl class. While googleing, I came across following article which demonstartes how to access Usercontrol properties in content pages.
Kiran Chand's blog
There was nother problem related to ImageButton. Somehow the server side click event of the image button was not getting fired. After trying all the stunts, I wrote to the ASP.NET team members and also to the authors who write articles on various sites. The answer I got from one of the ASP.NET team member was that the new version does not support multiple forms in the same page. And to achive the kind of functionality (search across pages) can be achieved using the newly added cross-page postback feature. For the time being that has solved the issue for me and I am back to giving finishing touches to the Petshop application.