I have a 2015 2.6/8/1TB mini and the speed is noticeably slower than my MBPr and MBA. I assume, based primarily on my MBA, that this is a result of the 1TB HDD. The mini is running OS X server and is used as a media center, Plex server, local iTunes storage, and for Time Machine. For all those it works fine. My only complaint is that when I'm opening software or restarting the system it runs slower than I would like; so Ive decided to upgrade the HD. My question is the extra cost for PCIe Flash based HD (PCIe flex cable & blade off of eBay) worth the cost over a cheap Sata SSD. I don't need the extra space in the mini as all my media is external so retaining the HDD is not an issue.