I have flashed both my U3S and QCX using this procedure. The only glitch in the doc is in Step 4e "Select ATmega328 as the MCU" It should be ATmega328P. I believe Hans has stated this is the chip they usually ship.
Sometimes we use ATmega328, sometimes ATmega328P. It depends only on availability and price, at the time I am purchasing the chips. They are equivalent for the purposes of QRP Labs kits. So if you get a message about the device signature being wrong, just change the chip name selection (or the name in the command if using a avrdude at the command line), try the other one.
