Check out Jossef’s post here http://blogs.msdn.com/jgoldb/archive/2008/01/23/vista-layered-windows-performance-hotfix-now-available-on-microsoft-download-center.aspx 

This is great news as you used to have to jump through some hoops to get access to this hotfix… But now its just a couple clicks away…

We have used this in some of our projects that need non rectangular window support. The animation speed with and without this patch is a night and day difference.