[javert]

A lot of what you're saying hinges on being specific to what you call "really scalable network applications," but you never said anything about that in your post.

(d) How is "multi-core doesn't mean multi-threaded"??? Snort is a multi-core app today and isn't multi-threaded.

This is, again, between whether you want to be "computer science correct," or use developer lingo that is not even necessarily consistent among all developer and OS subcultures. I think saying it the way you are saying it, instead of "You could use multiple processes to get parallelism, instead of multiple threads," is misleading.

What does your code scale to?

Well, I'm a real-time guy, so my thread scales down to microsecond overheads.

Did you change the text in your post that explains pthread_mutex_t? If not, I probably made a mistake to pick on that, because what you have there is pretty clear.