Sadly, I killed my 2012 MBP the other day (entirely my fault and almost certainly fatal), and I've had to rush to get another MBP up and running. Luckily, with the old design I was able to remove the SSD and it's in good working order. The replacement MBP is one of the 2016 models, so only USB-C/TB3 ports, but I've been able to boot to the old SSD without too many issues after running around and getting a variety of dongles... (still looking for a USB-C to SATA cable, they do exist but not stocked in stores yet). I am very tempted to keep two boot disks - the internal SSD and this external SSD. Some of the dreck that I've accumulated over the years can be left there, while I keep the new MBP fairly pristine. I am also sadly having some issues with the new MBP so it may be headed back (that's for another thread). What are the technical impacts of doing this? I already see that licensing is impacted, as Parallels is asking for a key even though it's fully licensed. I would guess that some apps write files/preferences and such directly to the internal drive. (as a side note I've run into install issues when there's only one boot drive, and it's external) Anything I should be aware of that might bite me sooner or later?