With respect, its this kind of talk which puts some people off of aikido. "Aikido is a lifelong persuit", "some techniques will take 20years to learn", "what is the definition of effectiveness"
It's not a hard question to answer, and i would answer Toms question as NO. If you're looking for a martial art to use purely as self defence. Aikido personally is the last one you should go for. Due to the amount of time it takes to grasp as opposed to something like Boxing, Kickboxing etc.
However if you're after something with a bit more spirituality to it, and something that will craft you over many years to become more aware to situation as well as an extra little tool in your belt if you ever do need to defend yourself, then Aikido would be good for you mate.
But i wouldnt recommend Aikido for instant basic self defence, take up something nice and simple and easy. Like one of the arts mentioned above.
I have a problem with such a response.
While intellectually, I agree with you, actual experiance has shown more then one student of my teacher and my friends, came to the dojo and told us of an attack he faced and repelled using the things he learned in the dojo.
I have also heard of failures, mostly attributed, byu the person himself, to his not doing something we practice.
It might be a matter of culture (Israeli people are often pro-action, so the technique might be more missing compared to the initiative\agrresive aspect) or maybe of a great teacher who has vast experiance with other M.A. too, and so really understands what he is talking about, and successfuly transmits it to his student\teachers or maybe even of Korindo Aikido being less simbolic in its techniques and closer to reality from the start.
Or possibly, the same situation exists in many other Aikido Dojo's only they do not boter to write about it.