I've been asked if I prefer the Senate's version of the "public option" (one which states can opt out of) to the House's.
The answer is not really.
The problem with an "opt-out" principle is that even if you don't think ANYONE should have a public option, you'd be stupid not to take the public option if everyone else is taking the public option, because your state's taxpayers are paying for part of it either way.
Thus, even if you oppose a public option, it is completely irrational to opt-out. You'd be better off if nobody (not you or anyone else) had a public option, but if you can only control your own state, and other states have the public option, you are better off having it than not having it. Thus, an "opt-out" public option is no better than a true public option.
The reason why it may be a little bit better is that voters aren't always rational, so if they shoot down the public option on principle, we'd be marginally better off for a while (until the state decides to opt-in, which is almost inevitable eventually). The other problem is that enrolling 70% of the country in one health plan run by politicians seeking reelection, not good and fair medical care and medical progress, is that the market power issue is not appreciably better than if 100% of the country were enrolled. This poses an existential threat to things like medical R+D and other medical research, abortion and quality and quantity of doctors.
(and yes, a public option will eventually capture 100% of the country... it may take a while, but it's also almost inevitable. If taxpayers are going to be supporting the public option, why would I pay partial medical premiums to the public option through taxes and full premiums to my private insurance when I can receive insurance from the public option for just one full set of medical premiums? Another example of "I'm better off if I don't have it and nobody else has it, but once everyone else has it, I basically don't have a choice")