I spent a couple hours today and yesterday attempting to assemble Rev1 of this board. The two board components that were extremely difficult to do by hand without the proper microscope for viewing were the microUSB port and of course the SAMD21, which in the 48-pin TQFP package was very difficult to do without jumping pins together with solder. All the other components, all 0805 handsolderable footprints with 1 crystal, reset button, and voltage regulator, were easy to assemble.

The next stage in assembly was to upload the bootloader to the SAMD21. I did this by following a great tutorial from Adafruit titled: How to Program SAMD Bootloaders. After fixing some connection issues, I finally managed to upload the bootloader to the SAMD21. After booting up the Arduino IDE and uploading the basic blink sketch, I can verify that it works! I'm very happy about this, given the amount of time I invested into the design and assembly.

Attached below are some photos of the assembled board, both powered and unpowered.