I think this is supposed to be a winter salad. Am I late in recommending this? I've heard it's still wintery in some parts of this country.
In any case, whenever the produce stars align and I find that we have avocado and arugula (always) and beets and grapefruit (sometimes), I am compelled to eat this combo. Add a little olive oil and maybe some crumbly salty feta and you're golden.