Business Insider (hardly a hotbed of communism) eviscerates Republican arguments against President Obama Millionaire Tax.
The highest marginal tax rate was 50% during most of the sainted Ronald Reagan's reign. During the halcyon days of the 1950's that Tea Partiers look back to longingly the tax rate reached over 90%. While Obama has not been specific, I doubt he plans to reach those levels.
Still, be prepared for a cascade of whining from the GOP that taxing the wealthy a bit more than they pay now is unfair, class warfare, and will cause the Koch brothers to curl up into fetal position and poutingly go Galt.