Really? It seems silly to have a variable available to change without any indication that you need to change another to get the change to really work. There seems to be no reason why a custom firmware like Tomato or DD-wrt wouldn't just default to the highest Tx power country setting, or bypass this altogether.
Also, I seem to remember a note indicating the range can go from 1-249mW. This would be an opportune place to indicate "Change your region for higher than XX mW"