I've been wearing the LLBean turtleneck and mock turtle now for more years than I can remember. Every once in a while I stray to another brand and always spank myself for it. The material is comfortable, shirts maintain their shape and color, and they are a mainstay in my cool and cold weather wardrobe. I recommend them enthusiastically.
I purchased several mock turtlenecks and found them to be comfortable and of high quality. I returned them for this reason alone: I am a thin person and the necks, which I like snug, were loose around my neck. Perhaps adding a bit of spandex to the neck would help. But then again, some people may like a looser neck. I don't.