A new Channel9 video has been posted that I wanted to link to here. The video is located at https://channel9.msdn.com/ShowPost.aspx?PostID=374129, and in it, Robert Flaming discusses application compatibility issues that can affect Windows Installer-based setups on Windows Vista and Windows Server 2008.
If you are a setup developer and will be targeting Windows Vista or Windows Server 2008 for your MSI-based setup, I encourage you to check out this video.
One of the key application compatibility challenges that Robert discusses in this video is how to author custom actions that will interact correctly with UAC on Windows Vista and Windows Server 2008. Robert has written a series of blog posts that contain much more detail about how Windows Installer interacts with UAC, and I encourage you to also review these posts if you are creating MSIs that will install on Windows Vista and/or Windows Server 2008.