Here is a cool success story I thought I'd share:
"We find Diskeeper to be vital and we use it for our virtual servers (VMware) as well. We redirect our user desktops and My Documents folders to network shares and have found the response times improved quite a bit after defragging the virtual server. We also found that it cuts the time needed to perform a P2V (convert physical machines to virtual) by about 90% if the physical server is defragged beforehand. Case in point, we had a few physical Citrix servers that simply did not want to P2V but simply worked as expected after defrag and very quickly. Thank you Diskeeper."
Turner Padget Graham and Laney, https://www.turnerpadget.com/