The short version, quite to my surprise, is that Chief Justice Roberts bought into essentially the same logic that I'd been thinking: call it what you will, the "individual mandate" is effectively a tax, and pretty obviously constitutional on that basis. I suspect that that is going to make for all sorts of entertaining politics in the coming months as Romney jumps up and down going, "Hah! See! Taxes!", but I agree with the reasoning, and appreciate the general call-a-spade-a-spade attitude.
Anyway, the article is fascinating, making the point that this is remarkably clever of Roberts politically: instead of the sort of knee-jerk reactionary rhetoric that we've been seeing from most conservatives, he's made the Court look a bit more reasonable and less partisan, while winning a much more important conservative victory by bounding the Commerce Clause a bit.
So overall, a good day for the spirit of compromise. The Administration wins what will probably be its most important political battle, but the conservatives force them to admit that it's a tax. The horrible health care mess takes at least a baby step towards rationality for the first time in decades, and I breathe a quiet sigh of relief. (No, I don't love the Obamacare model, but I think it's still a major improvement over what we've been dealing with heretofore. If we can't get a genuinely sensible single-payer model, at least we can make what we *do* have suck less.)