I'd definitely be for a graduated tax rate for capital gains. Would generate a lot of revenue and a good place to get it from.
The argument against it is that if you tax capital gains higher then you discourage people from investing their capital in the market, but if we're talking about a graduated rate, it means that you can target the highest rates at the people who are making a ton. If we raise capital gains taxes for the people who are pulling in boatloads, I'm not worried that they'll take their millions and hide it under the mattress rather than investing it.