So I finally did that thinning at the garden. Came home with this big plate of beet greens. (Yes, really, my seeding technique is THAT bad.)
I had some pancetta, so I sauted that with some onions and then I threw the greens in. I did trim off most of the heavier stems and roots before I threw them in the pan. Shortly after adding the greens, I poured in a mixture of sugar and cider apple vinegar--less than a 1/4 cup.
All in all, I'd say...eh. It's definitely an earthy flavor. Maybe I would have liked it more with bacon and less vinegar.