I've used these on a few of my projects making replacement parts for vintage computers. They are a nice way to make a board which is no larger than a 40 pin DIP IC and will fit in most types of sockets without damaging them.
A couple of requests for future versions, it would be useful if the carriers were joined in pairs with 0.6" or 0.3" spacing, so you could just sit a board on and solder, and both sides would be correctly space and straight. Also for me it would be preferable if the pins stuck up out of the PCB to make soldering easier.
There is a longer review and some pictures on my blog: http://blog.tynemouthsoftware.co.uk/2017/02/flip-pins-review.html
Dear other readers, Dave's longer review (including some negatives) is well worth reading, and I have written a far more detailed reply on his blog site. There are some great pictures there too, of his use of Flip-Pins