I'm using Defraggler 2.18.945 (64-bit). I noticed that a recent update has added the Statistics tab, so I used it to measure the performance of all my drives. And they are not at all what I'd expect.
My PC has three SATA/300 drives, C, S and T. There is also a USB2 hard drive plugged in - drive J.
I'd expect C, S and T to have fairly similar speeds, and J to be somewhat slower.
But the graph of the speeds (see attached) shows the C drive to be very slow and the speeds of S and T to be much faster. On several different runs, S is sometimes faster than T and sometimes slower: the example shown here has S=116 MB/sec and T=84 MB/sec. C, the system drive, is 1.3 MB/sec - VERY slow.
When I've copied large (eg 1GB) files between two folders on the same drive, I've found that all three drives are about 30-50 MB/sec. J, the USB drive, is about 20 MB/sec.
Sadly the help files at http://www.piriform.com/docs/defraggler don't mention the various tabs such as Health and Statistics - I wonder if they need to be updated to keep pace with the product :-)
All four drives are NTFS, by the way.