There is only one way to know if your aikido works in the case of a real attack, and that is to hang around in a shady part of town until someone attacks you. I'm going to go ahead and guess that no one in this thread has done that, and that therefore that a style vs. style effectiveness argument has nowhere to go but down.
Unfortunately, in my work I deal with everyday people who have been involved in attacks, domestics disputes, and many other unpleasant situations. One does not have to hang out with shady characters or the bad area of town to experience violence that's in your face. Certainly, that can increase your chances, but it is not necessary. Therefore, IMO one cannot afford to not at least strive to make one's training as realistic and practical as possible. That is not to say that one's training has to be totally focused on that or that is all you should think about, but it should be a significant aspect.
On this forum and at seminars, I have often hear from a segment of the Aikido community that does not believe that self-defense is necessary. Besides, if one does include it, that it can't really be used against someone whose is trained or street experienced (some thugs really are) or it seems implied that if one does have that as a point of emphasis that you somehow forsake it as a means of self-improvement to become a better human being, marriage counseling, working with troubled youth and just plain having fun! It would seem that there is this fork in the training road that its either martial and that's all one can focus on or its the softer side of self-improvement and metaphorical uses. I still have yet to hear a convincing argument on why one can't and shouldn't have both sides as parts of one's training path. To be sure, " realistic" is subjective and is an approximation on a continuum.
However, unless one completely out of touch, its not that difficult to see how physical conflict happens in the 21st century (potentially to anyone anywhere) and how traditional approaches and techniques may have to be tweaked or modified to make them work. Moreover, it sometimes just comes down to martial intent on the Uke's and Nage's part and that is very difficult if not impossible, to teach.