This is really a headache tax system for upper middle-class only

The AMT capped at 28%, therefore, if someone paying margin tax rate at 35%, most likely he/she has no issue.

Higher local tax rate, high mortgate loan or 2nd house loan, too many dependents are all factors. 

this is a great article to understand it:

http://www.smartmoney.com/taxes/income/the-alternative-minimum-tax-9540/