The only "problem" with the Calhoon bullets is distribution and marketing. He doesn't sell to distributors, so they are sold "word of mouth" pretty much. You can't run down to the local shop and buy 100 to try out, so people are somewhat wary of them.
Calhoon boxes his bullets in 250 count packages, which "ups" the price, which also makes folks wary of them. I'd never have tried any, except a friend who lives close to Calhoon sent me a "box" of them for a slight favor I did (nothing worth a whole box of bullets, I'd have done it for nothing).
FWIW, the little .224" 37DHP is fun to play with in .223 rifles. I haven't gotten round to ordering any .20 bullets, yet, but I DO intend to order some bullets from him, some day. I just haven't needed any bullets this year, I haven't done enough shooting to justify buying anything at all. Oddly enough, I got better accuracy out of the 37s in my .223s than I did the .221 Fireball, which would seem to be better suited to such a light bullet.

. They sure kill a PD with authority, if the wind isn't blowing too much.
Build a man a fire, and he's warm for a day. Set a man on fire and he's warm for the rest of his life!