Re: How effective is aikido in self defense?
Awareness, plus knowing how to look simultaneously inoffensive and unafraid, are invaluable skills. I learned them as a teenager in NY decades before I ever bowed into the dojo. Steven B (welcome!)'s post reminded me of an incident in SF Mission district 32 or 33 yrs ago when I was walking home late alone one night and didn't like the looks of a fellow who was angling his walking path towards mine in an interception pattern. Without thinking I stepped down the curb between two cars and as his path came level with me, but now about 8 or 10 feet to the side, I simply raised my hands to shoulder level. His eyes widened, he sidled sideways away and picked up his pace to keep going.
Then there was the guy I scared the heck out of in the NY subway :-)
The nice thing now with aikido is I feel like I have something to back up my basic good instincts "just in case."