I'm using CM3 the dev board. I tried to make it boot from the network (I already did that with a pi 3) and I think I managed to brick the device.
It was booting from the flash nicely, but after a software update, it refused to boot. Of course, I tried to access the eMMC to flash a new image, but I couldn't anymore. Apparently this "program_usb_boot_mode=1" prevents one to access emmc. Is there a workaround?
I found this: viewtopic.php?t=179284 but I'm not sure it would work with the dev board...