Cilantro is a pretty plant any time -- bright green, delicate, excessively fragrant. But when it's in bloom, and luring bees and butterflies to the garden, it's a showstopper. I mean, I can't stay away. I just stand there and smile. So that alone would be worth letting a plant that takes up about a third of a raised bed take its sweet time going to seed.
But I'm hoping for more. This is in my permaculture bed, where I let about ten percent of everything go to seed or otherwise run its natural life cycle. I started planting it two seasons ago, and now I'm getting all sorts of happy volunteers -- kale, dozens of kinds of lettuces and greens, beets, and basil so far. I've also got some leeks in there that I'm letting go to seed, and redivide. This season I added chard, spinach, and tucked in some peppers, tomatillos and tomatoes. One nice result of this mixed bed is that pests never get a real foothold, as they might in a monoculture garden.