Wouldn't some of it depend on the purpose of the mortgage?  Was it a refinance so money could be pulled out to buy a boat, or pay tuition?  And how about the interest itself.  Is it limited on Schedule A, because of the amount?  But do those limits also apply to Form 8829?

Not a big issue for me because clients who don't want to claim the standard allowance, I send down the street.  But in these parts, it usually doesn't make much difference.