I keep a few in my box but I don't use them very often in the mtns. I've had success with brookies eating crystal meth eggs in pink or yellow. I also bought a pack of the clown egg mcfly foam, not to tie clown eggs, but just for the color variety. I tried tying them like I've seen in their videos but I thought them to be heavy when wet. Now i just wrap thread to the bend, tie in some mcfly, wrap back up, loosely fold the foam over, tie/whip/trim then fluff it out. Not a perfect sphere, but the holston trout didn't complain this past spring.
I tend to fish them in late fall through spring, weighted in moving water with some sort of indicator, dry fly otherwise.
I'm actually hoping you get more replies, I'm curious to see what the more seasoned dudes have to say