This year my itemized deductions were lower than the federal standard deduction, so I took the standard. When it came to my Massachusetts state return, unlike last year I was not asked for my deductible medical expenses. After some research I realized that the state only lets you claim medical expenses (after the usual 7.5% haircut) if you itemize at the federal level.
As this is all or nothing, it could make a difference to the total (federal+state) burden, but not only does TT not help you make that tradeoff, it doesn't even warn you to take the state situation into account. As it happens, I modeled the tradeoff and found that the standard deduction still minimized the total burden, but if the itemized deductions had been a little higher it might have gone the other way.
I'm smart enough to realize this and do the math, but others might be misled. Can you at least alert user in future?