No specific info about version 4.0. Please visit the main page of MyDefrag on Software Informer.
I, for one, did not experience any freezes, and the best thing about MyDefrag is that I can run it as a screensaver, so my drives get optimised "automatically" when I'm not using my PC during the day.
Terrific speed in completing operations.
The 'agreement' makes it clear they are planning to charge for it and if I have the older version I will use it and its very good, but I can't afford to pay for it.