What is Crossbow ?

Crossbow allows interoperability between windows forms and WPF.
This means you can use the great visual elements from WPF along side the windows forms bits that your used to, hence creating hybrid applications that use the strengths of both technologies.
So you could have a windows form app that loads in some WPF items using xaml etc or a wpf app that loads in a winforms datagridview etc.
It's still in beta but worth checking out to work out how you would be able to integrate into your applications in the future.
Check out this blog for more information http://blogs.msdn.com/mhendersblog/default.aspx