I'm not going to try to produce any detailed health care whip count of my own -- but I do think you can make a case that the Democrats have a reasonable-looking path to 216 votes.
To briefly recap the math: 220 Representatives voted for health care in November, and 215 voted against. Since then, four Representatives have retired (or died): 3 yea votes and 1 nay. That makes the baseline number 217-214, with 216 votes now needed for passage.
For the time being, the only people who look almost certain to switch from yes to no are those Representatives in the Stupak bloc who have concerns about the House bill's abortion language. However, the Stupak bloc is smaller than Democrats had feared, consisting of a half-dozen members rather than 10 or 12. According to both Chris Bowers and David Dayen, the "Stupak 6" are Bart Stupak himself, Joseph Cao (a Republican), Marion Berry, Kathy Dahlkemper, Joe Donnelly, and Dan Lipinski. Some of these members, such as Donnelly, are in tough districts and probably have reasons other than abortion to vote against the health care bill -- as I've said all along, I don't think the potential Stupak defectees are quite as pure-of-heart as they claim to be, but instead are weighing their objections to the abortion language against a whole number of other factors.
In any event, if she's out those six votes, Nancy Pelosi is down to 211 and needs to flip 5 no votes to pass the bill. David Dayen actually lists 6 former no voters in the lean yes category: Jason Altmire, Bart Gordon (retiring), Brian Baird (retiring), John Boccieri, Scott Murphy and Betsy Markey. Of these, I am skeptical of Markey and to a lesser extent Boccieri. On the other hand, the list does not include John Tanner -- another retiring member -- and there are perhaps a half-dozen other break-glass-in-case-of-emergency potential yes votes. I would not completely rule out Dennis Kucinich, for instance, whose district Obama is visiting tomorrow, even though he's a stubborn enough son-of-a-gun that efforts to pressure him into voting yes might only backfire.
On the other hand, there are quite a few other Congressmen who voted yes initially, and who aren't in the Stupak bloc, but whose votes aren't necessarily locked in. Dayen lists 20 such voters; other sources like The Hill, using what I'd consider to be a very ... inclusive ... methodology, list quite a few more than that. The thing is, though, that for the time being, you haven't really had any of these voters -- non-Stupak moderates who voted yes initially -- go on record against the bill. NY-24's Mike Arcuri had initially come the closest, but has since backed down from those remarks. I'd imagine that, for these Democrats, there is a fair amount of inertia against a switch: even in districts where the health care bill is relatively unpopular, flipping to no after having voted yes initially might not help them on balance between pissing off the Democratic establishment (see also: primary challenges, loss of fundraising) and making them join Blanche Lincoln at the Waffle House.
It seems to me that there are sort of two equilbiria: either essentially all of the non-Stupak yes votes hold, in which case health care passes very narrowly (perhaps with exactly 216 votes) -- or the floodgates open, there are a few key defections about half-way into the roll call, and anybody with a grievance deserts the bill, in which case all of the sudden it might struggle to get 200 votes. (Of course, Pelosi doesn't have to hold a vote, and would probably want to avoid such an embarrassing outcome -- but it's not out of the question that she could push the measure to the floor not knowing the result, and that things could totally unravel during the roll call.)
Right now, I'd place slightly more weight on the former case: that Pelosi holds together somewhere between 216 and 218 votes. For essentially the first time during the health care battle, all of the key Democratic constituencies are lined up behind the bill: the Congressional leadership, the White House, the unions, the non-Naderite activists. And when one cuts through all the clutter, the vote-counting news has basically been pretty good for the Demorats: (i) the Stupak bloc is toward the smaller end of its prospective range; (ii) some non-retiring no votes, such as Jason Altmire and Scott Murphy, have been openly flirting with a yes; (iii) none of the non-Stupak yes votes have yet flipped.
However, it wouldn't take much to tip the balance in the other direction, and I'm also building in a little bit of a self-hedge since I'm a supporter of the bill and that can color one's perceptions given such a subjective exercise. Right now, I'd consider the odds for passage to be no lower than 50 percent, and no higher than the 64 percent posited by Intrade.