I guess my comments should go here.  Board received 9/15; built up the PCB's week of 9/17; working on software week of 9/24 ; I've never used this particular MCU before, so I'm getting my segger j-link up and running - And I need to figure out how to get an LED to blink (I have a separate PCB that I designed a while back around this MCU, but never got around to building up experience on the toolchain, so now it's do or die time.)  I'm not a software guy, so this is going to be my stalling point, but I really need an ARM M0 in my personal component lineup, and I really like the feature set of the ATSAMD21 series.