I haven't actually used the SD card slot in my mid-2012 MBP more than a couple of times but recently read about how some people use it as a sort of SSD drive. I'm definitely going to replace the internal HDD with an SSD at some stage, but as it's not within my budget the SD card slot gave me some ideas..... 1) as an SSD with OSX and the apps on, then use the whole HDD for file storage. 2) as a Time Machine backup drive. This would be VERY useful IMHO as the drive would always be there (as opposed to attaching an external drive which is often forgotten, hence no regular backups) 3) as a smaller SSD when a real SSD can't be afforded. Not sure how much space OSX needs, and haven't checked SD card prices lately, but a relatively small/low costing SD card might be enough to hold OSX and the apps 4) a clone of the HDD (at least of OSX and the apps) -just in case the HDD stopped working and you'd at least have the ability to use the computer So I'm wondering how an SD card compares to an SSD when it comes to speed, data integrity and if it "wears out" quicker than an SSD?