The solution to this is the standard deduction of $5 a square foot, up to $1,500; claim all the interest and taxes allowed on Schedule A, if itemizing; and move on.  However, I realize that in some areas with high housing costs, or for some taxpayers who (claim to) use a high percentage of their home as an office, it's better to figure actual expenses.  Even if they must share with us in fees, half of what it saves in taxes, because of the additional effort required to compute it.

As I recall, the previous software I used allowed entry of 100% of interest and taxes on Schedule A, then carried over the appropriate amount to the 8829.  It drove me crazy (well, not quite) with ProSeries to have to start on the 8829 and let it do the work of carrying it over to the Schedule A.  Then Congress made it even more complicated, mostly with the $10,000 cap on taxes but for some people also the limits on mortgage interest.  

Why does IRS need two lines for real estate taxes on the 8829, anyway?  Did they put them there just to make it easier for programmers, who aren't taking advantage of the feature?