The DFU driver wasn't installed properly. Man, that's a lot of hoops to jump through! Anyway, that's fixed, everything shows up as expected in the Device Manager (driver version 5.2), updated successfully, re-flashed with blinky firmware, and nothing...
C:\Users\bblack>dfu-util -l
dfu-util 0.8
Copyright 2005-2009 Weston Schmidt, Harald Welte and OpenMoko Inc.
Copyright 2010-2014 Tormod Volden and Stefan Schmidt
This program is Free Software and has ABSOLUTELY NO WARRANTY
Please report bugs to dfu-util@lists.gnumonks.org
Found DFU: [2b04:d00a] ver=0200, devnum=11, cfg=1, intf=0, alt=1, name="@DCT Flash /0x00000000/01016Kg", serial="00000000010C"
Found DFU: [2b04:d00a] ver=0200, devnum=11, cfg=1, intf=0, alt=0, name="@Internal Flash /0x08000000/03016Ka,01016Kg,01064Kg,07*128Kg", serial="00000000010C"
C:\Users\bblack>particle update
Your device is ready for a system update.
This process should take about 30 seconds. Here goes!
! System firmware update successfully completed!
Your device should now restart automatically.
You may need to re-flash your application to the device.
C:\Users\bblack>particle flash --serial firmware.bin
! PROTIP: Hold the SETUP button on your device until it blinks blue!
? Press ENTER when your device is blinking BLUE
sending file: firmware.bin
Flash success!
I've tried different USB ports and different cables. However, since it's successfully flashing and updating the firmware, I would would be surprised if it were a port or cable problem, right?
What's next?