Ezra Klein posts a missive from MIT's Jonathan Gruber that, among other things, goes into some detail about what's happening in Massachusetts:

[Kit Seelye] then cites the experience of Massachusetts, where I serve on the Connector Board that is implementing our ambitious health reform passed in 2006. She correctly points out that, as part of a compromise last year, we exempted almost 20% of uninsured adults from mandated coverage. But half of these are low income individuals offered employer insurance who can be covered as part of the law, but for whom we have not yet had time to design an appropriate subsidy program. The other half are individuals above three times the poverty line who are excluded from subsidies through a compromise between then Governor Romney and our legislature. If subsidies were extended further, exemptions would have been unnecessary. Candidates Clinton and Edwards have said that under their plans all individuals would be subsidized so that no one has to pay an unaffordable amount for insurance. She has laid out no specific plans for mandate exemptions, and there is no reason why she should be tarred by what we have done under the constraints of our Massachusetts law.

This is a good double-corrective. On the one hand, the problems with the system in Massachusetts aren't as clear an indictment of the mandate-regulate-subsidize approach as I might have thought. on the other hand, this seems to me to emphasize the idea that the as-yet-undefined parts of the health care plans -- the scale of subsidies -- are very, very, very important to knowing what they look like in practice. The candidates are correct not to have attached meaningless numbers to their plans that'll just get washed away in congressional bargaining, but it's still worth recalling that this could go in any number of ways in practice depending on the balance of power in the congress.