Josh Marshall lays it out.
I would go a bit further and say that opting out will end up being an economic loser in the long run for any red states that choose to go that way, as new companies will probably be more likely to relocate to states with the public option.
At least, that's what I think will happen, because I think the public option is good policy. The nice thing about this compromise is that we'll be able to gather actual data that either refutes or supports that hypothesis.
In the short term, I don't think this is the best approach in terms of the public good, but I do think it might be better long term policy in terms of gathering data and building a strong national healthcare policy.