I'm an ex TKDist (WTF), witch some experience in competition in the late 80's, and now an 1st kyu in Aikido. When work schedule permits i train in American Kickboxing, and noticed Aikido principles are useful in the kickboxing environment.
However, i've also noticed kickboxing principles are also useful in the Aikido environment: hard physical training, footwork, distance, timing, pain tolerance and good "atemi" (especially as receiver of the "atemi"
) helps to make my Aikido better.
Of course i need more years of Aikido training to really say i have a decent Aikido.