As you know, we changed a few things in our underlying architecture for Clearspace 2.0, including some changes in the Freemarker templates as a result of moving from Webwork to Struts along with some other changes. In this video, Matt Walker, Professional Services Engineer at Jive Software, talks about the process of upgrading existing themes along with plenty of best practices to make your themes more easily upgradeable in the future.

Matt also did an earlier screencast as an Introduction to Skinning Clearspace, which you might also want to watch along with this video.

You can also download the Quicktime version (Caution: file is ~200MB), or you can watch a larger version online, which will improve readability of embedded screenshots (recommended).

The entire presentation is also attached below as a PDF file.