There are still plenty of days when Obamacare looks bad. Tuesday wasn’t one of them.

The Department of Health and Human Services announced that more insurers were joining the Affordable Care Act's new marketplaces—you know, the places where people can buy coverage on their own and, depending on their incomes, qualify for subsidies. How many more insurers are participating? Quite a few, it turns out. According to HHS, the net increase is more than 25 percent. That should translate to more options for people buying coverage. The increased competition should also help keep premiums relatively low.

The data is preliminary, based on 44 states for which HHS had information. And of course the sheer number of insurers offering coverage is just one sign of how the law is doing. If you’re actually buying insurance, you don’t simply want choices. You want good choices. You want to know that the insurance will give you access to doctors and hospitals when you need them. You want to know that the coverage pays your bills adequately. And so on.

Still, Obamacare critics hadn’t predicted the markets would evolve this way. On the contrary, they expected that that young and healthy people would stay far away from the new marketplaces, because the new coverage would be pricier than what they were paying before. Without enough business, the argument went, insurers would get skittish and withdraw. At best, the marketplaces would all become oligopolies and monopolies, with just a handful of insurers continuing to sell policies. At worst, the whole scheme would fall apart. That quite obviously isn’t happening.

Trouble could still arise. By design, Obamacare includes a series of provisions designed to insulate insurers from major losses in the first three years. I usually describe them as “shock absorbers.” Many other policy wonks refer to them as the three Rs, for reinsurance, risk corridors, and risk adjustment. Two of the three, risk corridors and reinsurance, are temporary measures set to expire in 2016. More knowledgeable critics of the law, like Bob Laszewski and Megan McArdle, have warned that more insurers could abandon the market or at least jack up their premiums once those measures expire.