For those folks who have custom Office solutions within their enterprise, one area that you often need to focus on during the upgrade cycle is testing out those custom solutions to make sure they'll run in the latest version. With Office 14, we're going to provide a great set of tools to make it even easier for folks tasked with deployment. Michael Kiselman provided a great overview today up on Gray Knowlton's blog: http://blogs.technet.com/gray_knowlton/archive/2009/10/22/announcing-the-office-2010-application-compatibility-program.aspx
We always focus heavily on testing application compatibility from version to version, and in most cases applications will continue to run just like they did in the older version. From time to time though there are cases where a custom application may need to be updated. The tools Michael describes help with both the discovery and migration processes.