I'm not crazy about them. I'm still waiting for blocks from 3 years ago from a swap in another group. Wouldn't have minded so much if it were only 1 or 2 blocks but it was an entire year's worth. She still posts with longer explanations of why she still hasn't done these. I'm not holding my breath. Another swap presented me with all sorts of sizes. Only one or two the correct one. I didn't expect perfection. Skill levels vary and all that can be expected is a person's best efforts, but like one of the earlier contributers to this thread, only a couple of the participants seemed to know how to use a ruler. I gave all of that swap away to a dog project ufo orphanage. They were way too much trouble to fix.
I've got too much of my own stuff to do and with the cost of postage these days, I'd rather spend my extra pennies on batting and thread.