Dear Toddsterpatriot,
Even with the AMT, I think that if nearly all your income is dividends from public companies, you're just going to pay the 15%. Mr. Gates will lose the deductibility of his local property taxes, and if he owns any tax-free bonds, some of them may lose their tax-free status (although others will not), but I don't think the rate changes on dividends.
A quick review from google shows that long-term capital gains rates remain the same under the AMT, and I'm guessing so do taxable dividends paid on shares in "C" companies.
I'm unclear about the limitations on charitable contributions, but I'm sure that Mr. Gates has structured these to take maximum advantage of tax laws. I think that the deductibility is limited to half of one's income for the given year (but that's from memory, I don't recall precisely).
By the way, I forgot that late last year, Microsoft declared an extraordinary dividend, which paid Mr. Gates somewhere around $3 billion.
sitetest
Don't forget his $1,000,000 salary. It's safe to say he paid more $$ and a higher rate than any soldier in Iraq.