As for left-handers, it can be easily be switched in System Preferences.
personally I don't think it would be counter-productive. Even after using WIndows machines for years, i have NEVER mis-clicked. When I first heard this "I hate accidentally right-clicking," I nearly laughed out loud. Maybe it only happens because you guys are too used to a large single button. As for myself, even on my MacBook, when I click, I ALWAYS click on the left side of the button. The right side is never touched. Guess I'm just used to it.
So I suppose it's preference, but like someone said before, the addition of a right-click button could attract switchers, and while it might inconvenience a few tried-and-true Mac users, it's really NOT an inconvenience or a nuisance to the majority of the people who will be using these machines in the future. It simply provides an alternative way to right-click. Anyone who wants to can continue to use their two-finger-single-click method, but for those who don't want to, the right-click button is there.
Just because you don't like it doesn't mean others don't. I'm not putting down the two-finger-single-click method at all, I think it's handy and it's great, but people like me would only use it because we have to, not because we want to. We'd rather have a dedicated button, no matter how great you think your way is.
That is all. Peace.