This is a little bit off the topic--

Which way ( jointly or separately) is better for married couple. This article is "comparing married file jointly" with 2 single tax filers. Readers has to be careful to distinguish them.

I did not see much benefit for couples who choose to file separately. The only thing it mentioned the one side has a higher medical expense (above 7.5%) for itemized deduction. Since it did not mentioned my thought about AMT, I guess there is not much benefit either.