Re: How many have switched to Carniolan?
As to the comb building, carniolans will build comb. But they don't do anything unless there's a flow. If you want bees building comb etc with a patchy flow, italians may be best. That's how carniolans are more economical the flow stops so do they.
For me though I'm using a hybrid around 3/4 carniolan 1/4 italian. A nice bee and to some extent the best of both worlds. Swarm prone would be the only draw back.
44 years, been commercial, outfits up to 4000 hives, now 120 hives and 200 nucs as a hobby, selling bees. T (mostly).