After testing.
If we enable the "startup/boot optimization", this allows the defragmentation of the boot files by consolidating file fragments and speeding up the access in the bootstrap's step (starting machine) and so speeding up the startup time of your computer.
The defragmentation of the boot files works exactly the same as the defragmentation of the hard disk but, the only difference, is that the boot files defrag is a different process and KD does a good job.
The first reboot, after I have flagged the startup optimization, has been rather long, at least on my PC, a few minutes.
Subsequent reboots instead were faster.
I tested KD in all of its functions and I haven't had any problem, registry cleaner, tweaks, files cleaner, all good and no "surprise" after reboot.
I have also used the internet booster function and it hasn't caused problem but the connection speed remained unchanged (in the short test period).
The database of algorithms and kernel is very often updated and this allows you to keep reliable the app.
Yesterday, a few minutes after a full cleaning, a pop-up appeared showing me that a file was restored, probably because of error, but this means a constant support: very good!