wildaikido

I would like to start with a quote
"The difference between a real fight and sparring on the mat is the difference between swimming in the ocean and swimming on the mat." Steven Seagal.
This is a very important point. You must realize that there is a difference between your Aikido 'practice' and what you would use for self-defense. One of the main reasons we don't train to realistically on the mats is so we don't get hurt. Also we are sometimes more interested in the 'budo', and not the 'bujutsu' (please no arguments or discussions on the do jutsu thing), this is simply because we are also trying to develop the self, and not just the techniques.
There is an interesting story in Roy Suenaka's book Complete Aikido where a large guy came into one of his dojos and said Aikido doesn't work because when Mr. Suenaka tried to do a kote mawashi (nikyo) on him he resisted. Then Mr. Suenaka said something like 'this is not what I would do on the street' and the guy said 'well do that then' so Mr. Suenaka broke his nose and then applied the lock most effectively.
Don't get me wrong I practice the self-development and study the philosophy of Aikido by my self in addition to what I practice in class. But I also make sure ALL of what I do is effective for self defense and this only requires a little extra thought, and yes atemi is part of this.

Hagen, to answer some of your points, I think you don't understand non-aggressive, this means you are simply not aggressive. I mean you can strike to the face of your uke and not be aggressive, also you can pin with great pain to him and not be aggressive. That is what is meant by non-aggressive simply don't lower your self to an animalistic level and want to maim or hurt your uke unnecessarily or out of spit. When you see some pictures of O'sensei you notice him smile as he applies a lock, this is being non aggressive, you will also notice that his uke will probably have a very painfully look on his face.
When it comes to fight someone who has a martial arts background, firstly this should not be that common. Any way to strike you he must get with in your ma ai past your comfort zone. When he does, strike first then throw him or apply a lock, it is still self-defense, legally aswell.
Remember that in Aikido we try and start by talking, 'verbal Aikido' if you like. But if someone comes at me moving like a boxer and I tell him to leave me alone, and he doesn't then I will do what I have to before he hits me. Not many boxer over committee there attacks and they snap back quick so atemi again is important. Irimi is the only thing to use against people like this, as tenkan movements will not work.
Speed has noting to do with Aikido only timing, study this.
Andrew a great point, Aikido is not about applying techniques it's about applying principles, study this.
Jun, the best point so far, "Aikido works. Your aikido may not work. Please understand the difference..."
If any one has any questions about my rather long dribble then just ask.