The tax deduction appears to only apply to mortgages that were closed in 2007. If you had a loan with mortgage insurance in 2006, you won't be able to deduct the premiums for the 2007-2010 tax year unless you refinanced in 2007. There are also income limits. You get the full deduction if your adjusted gross income is $100,000 or less. The amount you can deduct phases out rapidly after that, and no mortgage insurance deduction is available if you make more than $110,000.
You should also consult a tax professional to confirm what I have provided here is completely accurate (everything is in a state of fluctuation these days).