Here's what I'm finding, and it seems marriage is a benefit in some cases and a penalty in others. It depends on your personal financial situation.
"Now, as for getting married or not, that's almost always a personal decision instead of a tax decision. Strictly from a tax perspective, getting married makes the most sense when one spouse earns income and the other spouse doesn't earn income. That because one income is being spread over two people, and the income is now tax at the more favorable Married Filing Joint tax rates, and the married couple can enjoy higher limitations on retirement savings and other tax benefits. Again, strictly from a tax perspective, staying single makes the most sense when both life-partners earn income. That's because you can use different tax strategies for each partner. For example, the person with the lower income can take advantage of various child-related tax benefits (head of household filing status, child tax credit, earned income credit), while the person with the higher income can take advantage of various income-related tax strategies (as I discussed above)."
from
http://taxes.about.com/od/taxplanning/qt/m
arriage_tax.htm
Again, not that I'm denying that married people get multiple other benefits.