Aside from the Nibco ordeal, I haven't heard of any issues myself. Kitec had a delamination/separation/rupture issue and huge settlement but that's PAP. Been using B myself since day one with no issues, really don't see where it could go wrong unless severely overheated. I've had to pull a lot of crimped joints apart and even with the ring already cut off it's tough to separate without heat. Re-plumbed some stuff for my old man last fall after an underground Logstor mishap/replacement and noticed there was a coupling near his boiler that the last guy (me) cut the ring off of to separate and apparently had a change of plans so the ring never got replaced. 4 or 5 years ago when that boiler was swapped in. Granted it's just atmospheric pressure and was a return line, but the stupid thing went 4-5 years with no ring and never leaked a drop. Pretty impressive if you ask me! I don't much care for the poly fittings unless they're couplings, have seen enough of them break that I don't care to use them. Customer recently came and bought some PEX-B
from me to replace a blowout in his basement. Said his existing stuff was green (I assume Central pex? Which is B) and his aquatherm in the garage overheated. Blew both relief valves AND split the pex in the basement open like an overcooked hot dog. Still racking my brain to figure out how exactly that can happen with reliefs in place which also went, but it did.
Ever play with that polybutylene crap? What a dumpster fire. Sharkbite is the only thing I can find that works on it. I was able to crimp it once with double rings, crimped the first one like normal but it was still loose, so I split a second ring and put it over the first one and crimped again. It's only been a few months but it's working well so far! I saw some of that junk once in a basement that was so brittle from the heat over the years, that it shattered like glass when I tried to bend it in about a 4 foot radius