Yes, by my own hands
I used a combination of a DIY video on MacSales dot com and another site (can't remember off the top of my head). I ordered the OWC 240Mb with USB 3.0 case, and then wondered, "Why is it only transferring at about 14Mbps?" and then a quick google search and a Apple.com visit showed: Mac Mini is 2.0.
For the comment an external is as fast, that's not the case unless you possibly get a firewire 800 case. Besides, it defeats one of the main advantages of a built in SSD drive: ease and speed.
I used the 5 piece kit sold by said website above and had all the tools I needed. I did it in about an hour, start to finish. I took my time. Boot time went from about 45-50 seconds (i5, 8Gb RAM, 2.3 GHz CPU) to 15 seconds. No application ever bounces in the dock while waiting, which is misleading because there is no wait. I'd do it again and it's not terribly hard. Just take your time, watch the video's 2-3 times BEFORE you start and take pictures at each step. If you forget how something was, you have a picture.
I also wrestled with spending the 60$ or so for a dual drive cable that the server model comes with and decided to pass for 2 reasons: not worth the hassle to redo the install, on principle because it seems everyone has gouged the hell out of the price.
My read write speed tests are about 560Mbps on read and write with the 6G (not Pro).