One feature I remember from MusicMatch which I miss in Media Center is the "Watch Folders" option - basically you would tell MM to monitor a defined list of folders for changes, and it would automatically update/import files as appropriate.
The way this feature would work is as follows - you'd have an option to define what folders you use to store your music, that you want MC to keep track of.
Then, with the press of a button, MC would:
1) Carry out an "update" operation on all files in those folders (they have those folders in their filename path, in the database) using settings from the last update
2) Carry out an import operation, once again using the default settings from the last operation
For bonus points, use the Media Scheduler to trigger this operation (maybe it can do this already?)
For even more bonus points, add a feature to "update library" that looks for files that have been moved - use the defined folder list to narrow the scope ie. look only for files that were in the "watched" folders, and if they're not where they're supposed to be, search for them only within the watched folders.