I used to train in kendo, and I did find that I had to de-learn some of the postures, as it affected my aikido. For instance the fact that in kendo you always have to keep you back heel up posed large problems.
Ive heard of yari used in certain aikido clubs. Id love to learn yarijutsu and naginatajutsu, it looks so gracefull. I saw a kyudo demonstration on Eurosport, and it blew my mind. They were hitting targets while moving on horseback and blindfolded. It looked incredible.