If ChronoSync 3.3.6 impressed with its speed and ease of use, its nimble flexibility and total reliability, ChronoSync 4.0.1 disappoints greatly. It is a slow and clumsy beast, and constantly chokes ("spinning beach ball," hurray!); it always asks for Keychain access - even when the option 'Always allow' is checked, ChronoSync repeatedly asks for permission to access Keychain! And without giving it that permission by clicking the appropriate button, it will not start. This is just one of the many bugs this version suffers from. But the most questionable flaw is its inability to automatically back up data, despite the schedule being properly set. No matter what I tried, ChronoSync 4.0.1 would not work in the background - it has to be activated manually, and manually only was I able to back up data. Perhaps it is my own fault, I do not know. But what I know is this: once version 3.3.6 was set according to my wishes, it worked perfectly (five stars, period). Version 4.0.1 deserves half a star, at best. Not worth your money. Hold on to the older version until the developer makes the programme usable. For now, it is not even a beta version.