Do NOT use OptmUSB if you have any other files or directories on the disk that begin with a dot. I tried it on a media player with Rockbox installed, which puts all its system files in a directory called ".rockbox".

OptmUSB seems to delete all files it finds with names starting with a dot, irrespective of whether they are the special Mac OS trashes/Spotlight/fsevents files. Anyone who stores preferences from UNIX style programs on a USB stick will also fall foul of this, since the convention there is to name settings files starting with a dot. Web developers will lose files like .htaccess, etc.

You have been warned.