DOMA is a tax nightmare. If you want to simplify people's taxes, repeal it and let states define marriage as they always have in the past.

The article you linked to did not mention that some businesses now keep two sets of books: one for state taxes, the other for federal taxes. The companies need to keep track of which deductions they can take in the state that are not allowed at the federal level. It creates a silly amount of accounting that lines the pockets of the Big Four accounting firms and pretty much no one else.