I find your post one of the more thought-provoking and substantial posted here lately. As MeeraReed said, there's certainly been a glut of silly and shallow posts here lately. I would add that reading here in the last month would not convince me that poly is about 'love' or relationships, since it seems lately most posts are all about sex.
I think your post faces honestly the real problems with poly, and that these points will be remembered before anyone posts that others are 'afraid' to try poly, or somehow narrow minded or ignorant or prejudiced against it. I don't know, maybe someone somewhere is, but plenty of people will refuse to be involved because there are good reasons not to be. As highlighted in your posts.
Regarding number four, I went into dating a married poly man in the wake of divorce due to infidelity, thinking if the wife knows and agrees, then the dishonesty that makes infidelity such a big problem is gone. His attitude was that someone would come along and sweep me off my feet and why not enjoy dinner and theater together until that happens. I enjoy it, he enjoys it, his wife loves that he's got someone to occupy him while she's off doing her thing.
But the reality slowly dawned on me as I have dated other men. I haven't been attracted enough to anyone to go on more than two or three dates, so it simply hasn't come up. But I have come to understand that many people will be turned off by the fact that I have dated a married man. I'm not going to call them names for it--they have every right to have their values, standards, and beliefs. And doing so wouldn't change the reality, anyway. By dating him, I have quite likely, limited the pool of people who will be willing to date me in the future.