With practice it can be very effective and you MUST use Atemi in your practice if you expect your Aikido to be effective against other Martal Arts. To say it can be effective without it is to ignore reality.
Ha - can't resist.
It amazes me that you think your reality is the only valid one.
Live long and prosper. Don't train with me. You'd hate it. You can't hit anyone. :-)
I'm not talking about the UFC, by the way....