I've used Aikido techniques in several situations where the individual trying to cause me harm was a grappler / wrestler. Just as Mike stated in the above response, most grapplers and wrestlers do not respond well when confronted with an opponent who knows how to maintain proper distance. One encounter I had was during high school (many years ago), another student tried to "shoot" for my legs (a common wrestling takedown); as he bent over to reach for my legs, he left himself wide open for me to perform a very nice Kaitenage. Since that day, the wrestler (he was bigger than me and had supposedly won many trophies for his wrestling ability) has never even looked at me funny.
My point here is that Aikido can be used as self-defense, I know because I've proved it to myself and individuals who have tried to cause me harm. Aikido students do not train for competition (with the possible exception of Tomiki Aikido). The focus is on protecting yourself and becoming a better person, not on competition. I believe that a person must train diligently and have a strong grasp on the fundamentals in an art (whatever art it is) before they pass judgement on the arts effectiveness. It has been stated before, and I shall repeat it; It's not the martial art, but the martial artist.