I use PerfectDisk, and actually own a license, but i see a lot of potential in this great little program.
One of the main features i see missing is an offline defrag feature. The reason i say this is because there are certain files that Defraggler cannot defrag, as they are in use by Windows.
This may confuse newbies, since no matter how many times they defrag a file, the excess fragments won't disappear.
Anyway, that's my suggestion for this otherwise near perfect and compact program.
Really great work Piriform!