The TabItem doesn't changes when selected Item in the VS2010 designer.
The issue is present also in the VS2008 and Blend.
I use VS2010 + Silverlight and I can not select the tabs, it would be really helpful if this functionality as soon as possible.
It is Happening in WPF as well . And it is very annoying as you can't see contents of othr tab. Please fix this issue asap.