I found the following issue while upgrading one of my apps to beta 2. The Handled property of en event now stops bubbling, there is no support for using WPF handledEventsToo.
It's all clearly stated in the documentation, at the end of http://msdn.microsoft.com/en-us/library/cc189018(VS.95).aspx:
WPF has an additional available behavior that can continue an event route even if Handled is set to true in an event handler. For this behavior, only handlers registered with the special handledEventsToo value are invoked on elements further along a Handled route. Silverlight does not have an equivalent behavior to handledEventsToo, and no API for registering handlers in this way. If you set Handled< ...
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