I loaded ~12 Gigs of data into a workspace for testing. Afterwards, I deleted the workspace but the disk space is not reclaimed. A peek into the contentstore reveals that the bin files are still present. Am I missing something, like a purge command?
No, indeed, you have not missed anything. The issue has been resolved in the last few days, following some persistence and other code dependencies being resolved.
The version 1.2 (or current nightlies or source code) have the cleanup job installed and enabled. By default, it will move unused content to a contentstore.deleted content store, but this can easily be made to trash it completely.