Everything we do in aikido builds towards powerful, whole body movement. Normal aikido training will enable you to punch someone quite hard. It might be a little slower than some other arts that are oriented towards striking, but it will happen.
I agree. Aikido, by virtue of its instruction in body unity, does build toward powerful strikes. However, I still feel that one should practice the strikes specifically and everyday. Just because one can deliver a blow powerfully doesn't mean that it will be done properly, nor does it mean one won't injure oneself in the process. Try punching the bottom 1/8th of a heavy bag as hard as you possibly can. With a fist. While trying not to get hit, etc., etc. (Written by a practitioner of karate, so you will understand the source of my bias)