Watch for the WPF sandbox
If your coding a WPF app as a windows app and thinking about allowing it to work in the browser then be aware of the sandbox, this limits certain chunks of functionality for security reasons. This whitepaper
is worth printing out and keeping to one side when planning your application in the first instance or considering a browser move. Some chunks of functionality I am not sure why they are limited, bitmap effects for example, things will change I am sure.