I was lucky enough once to sit in FC on a J ticket from ICN-BKK. It looked like there were only 8 of us in business so they let us use the FC cabin. I sat in 2K but it seems to me that all the seats were pretty equal. I prefer row 2 since you're a little bit further away from the galley, but that's just a personal thing.

I can't speak to getting them to seat you in FC though. I think I've read here that it's possible, but I can't remember what the verdict was. For me I was able to pick the FC seat online about a month before my flight.