I've found in my aikido training that it is not an effective martial art to counter real life threats. Let's face it, there's no way to predict how an opponent will attack. All this "sensing ki in your opponent" is a load of b.s. The enemy is not going to attack shomenuchi, yokomenuchi, mune tsuki, kata dori, katate dori, ryote dori, or kosa dori. Your enemy is going to attack in a quick, unpredictable manner which probably doesn't set the aikidoka up for any functional counters. Even if the aikidoka manages to lock the opponent in nikyo, sankyo, or kote gaeshi, the enemy will simply take the pain of countering the technique, not merely submiss. Fists will be flailing, elbows flying, and shoes kicking.
Having this outlook on the lack of combat effectiveness of aikido, I practice the art for its positive spiritual nature, the friends, the peaceful yet strong philosophy, and the sheer fun of countering idealized attacks with locks, pins, and throws. Besides, the fact of the matter is, I will never be involved in a dangerous physical confrontation (as long as I keep my wife happy).