I have used several of the boards you mentioned and plan to eventually get around to a couple mentioned that I don't have yet. One new one I recently picked up was the Atmel ATSAMD20-XPRO for their new Cortex M0 processor.
I wanted to get some experience with the low end Cortex ARM processors. One thing that really pushed me towards the Atmel board was their free development system. It is based on Visual Studio, which admittedly is a hog but I am familiar with it, and it comes bundled with the GCC compiler already integrated.
Most of the other development boards require a higher end 3rd party development system that is either time limited, code space limited or cost several $K for the professional version. If I was working on a commercial product I might have gone a different route, but this is a self funded learning project that will probably extend over many months on a time as available basis.
It is really very diversified varieties of boards covered by one person. Raspberry-Pi and chipkit module combination will be really helpful stuff for armature electronics developers, otherwise if one know embedded system design he can directly program Raspberry-Pi. But overall it is very good video explanation of wide variety of boards.
As always Caleb I am amazed by the way you seemingly effortlessly jump between platforms. But it occurs to me that where I would have a few different chips and transistors on my workbench, guys like you now have a few different boards. Getting an MCU project going from scratch would be a huge undertaking these days, but the boards do most of the donkey work for you. The effort is now in the programming and interfacing (which is where you excel). Very nice show.