When I watch a directory, are all subdirectories watched as well?
Yes, all sub directories are watched, as well as any new directories added subsequently after switchboard has started watching a folder.
Try not to watch a folder with many many sub directories as you may encounter file system limitations on how many watchers you can have. Please see the limitations section for further info.
Why am I receiving multiple events for the same file on OS X?
Spotlight indexing on OS X can result in multiple events. A temporary workaround is to add your folder(s) to the Spotlight Privacy settings