I saw it today. I thought it was well done - Portman was extremely good. The one thing I'd say is that, while I understand, that for large portions of the film, her characterization was intended to be remote, I found something quite remote about the film itself - while I enjoyed it and appreciated it, I wasn't all that engaged by it.
Hopfeully its good but im always skeptical about biopics.
They're almost always horribly boring and cheesy despite all the nominations they get.
It's not cheesy at all. I also didn't find it boring (although I found it distant at times).
'Biopic' isn't a great descriptive of it - the movie covers the span of a few days (between JFK's death and funeral) and her subsequent interview with Life Magazine.