Significant (and relevant) discussion on all three.
(And in re-reading one of those threads to make sure it was relevant I'm reminded that some people don't want me to cross-reference stuff. I find it hard, as I see it as a way of creating value by preventing duplication and re-raising previous discussions. But I'll stop again. Like an addict no doubt I'll start again, but I'll try not to. See my profile for more information (if you care))