I have a lot of files to sync where (sometimes) only the contents change, not the file size and date. To make really sure that the files have actually been backed up I have to set the check contents option.
This really slows down the syncing of course. However, an option to check only a part of the file would really improve things. For example, check only the first and/or last 4096 (or any other number of) bytes would really save a lot of time because that's where the metadata is stored which has been changed (mp3 , jpg etc.). A knowledgable user could save a lot of time here by setting this option!
Also, I hope that a future release will add an option to verify if the copied file has been correctly been written to the destination device.
thanks!