I just wanted to note that the folder this cleans up is created by libdvdcss, and contains the decryption keys to all the DVDs MTR (and also VLC, if you use that for DVD playback) has processed in the past. The keys are kept to make any future processing of the same DVD faster. We run this same script (along with one to delete the preferences file) every time you launch a new release of MTR for the first time. If demand is high enough, we could have MTR clear this folder each time it's used, however, since it's also shared with VLC, we'd be treading on their turf as well. If you want this functionality to become part of MTR, or don't want it to be included by default, please let us know at mtr@wormintheapple.gr