The SJ21 is my dream boat. Went with a Bucc18 for now; a little bit easier to trailer and launch. Love the SJ's heavy swing keel & that it is both fast and forgiving. Bet it's easier to single-hand than our Bucc.
I am sailing a Bucc this Saturday to take the kids out to watch some other kids race Optis. I sailed it once before (belongs to a nice guy in a local club) and was pretty impressed with how it handled. I had crew, but the boat I was on was set up pretty well for single handed sailing with the quick set/release jib cleats so you would just whip one free as you started the tack then pull and cleat the other as you came about. But if they needed fiddling with it would be a pain. It was just far enough away that you don't have a lot of leverage on the tiller.