I plan to upgrade XPro to MC. Will the process endanger projects and media already on the XPro system? What's been your experience? Thanks for any insight you might have on this.

Projects and user data have always been separate from the application installation. Depending on what you are upgrading from, you may have to point the new software to the actual locations of the Avid project file but they will not be removed or disturbed by the uninstall/install process.

 One other thing that may help on the subject of projects. Prior to installing MC soft, back your projects up to a different location and then, after your AXP uninstall, delete all empty folders to do with avid as well. I forgot to delete the shared avid projects folder in my documents, so my MC installed over the top of the old projects. Had terrible trouble with EDL manager until I uninstalled again (remembering to delete the projects folder this time) and did a fresh re-install. Now edl manager plays nice. 

HTH

Here's my recommendation, based on years of bringing projects from production companies home to my Xpress Pro system to work on, and then back to them again (I'm currently doing that weekly on an eight month job for Spike TV).

Don't move your Xpress Pro projects to where Media Composer can access them. Instead, create new projects in Media Composer, and then at the file level (Windows Explorer, or with folders opened individually in My Computer), drag or copy the BINS from your old projects into the new, equivalent MC projects. It's quick and easy to do, and you won't run into any little incompatibilities at the project level. The bins and media will definitely be compatible.

My projects appeared automatically when I upgraded and opened MC 2.8.