Nice article and I'd like to ad that okonomiyaki is not just a Kansai (Osaka) specialty, but also Hiroshima, which always includes the noodles.
A few other corrections I'd like to point out would be that, no matter how many times I've had okonomiyaki from one end of the country to the other, I've never seen it cut up like pizza. You are given some large spatulas if you choose to cook it yourself, and some smaller ones so that you can cut it up on the griddle in squares which you then put on your plate and top with okonomiyaki sauce and mayonnaise. The shaved bonito adds a little festivity by dancing on top when applied. Great flavor too.
If you're in Kyoto you can find a restaurant called Issen Yoshoku, which is the older name for okonomiyaki, and a pretty enjoyable place to learn more about its history.
In Tokyo you'll usually find okonomiyaki paired up with monjayaki, which could be seen as a variation. I didn't care for the latter nearly as much until a couple years ago. For monjayaki definitely take a side trip to Tsukishima.