Felix I have not, my time has been mostly spent in the Cheonan-Asan area on the west coast, with day trips into Seoul. I'd like to see more of the provinces this time. I was in Busan overnight to catch a ferry to Tsushima for a day, and got around okay, but yes, the Japanese are fairly monolingual, though it seems they understand quite a bit, particularly in writing, but are reticent to use less-than-perfect English. Also visited the DMZ twice, which is surreal.
With the sole exception of some pungent seafood I have always greatly enjoyed the food throughout East Asia. So far I've been to Japan, Korea, Taiwan, and Hong Kong, and I've always eaten well for quite reasonable prices, even at Michelin-starred restaurants. Gourmands could do far worse than East Asia.