If one ignores FICA (social security) taxes, the US has a negative income tax for the lowest income brackets. I think this is a wonderful thing in that it encourages low income people to get into and stay in the workforce, and encourages high income people to focus on investment, due to lower taxes on long-term capital gains.

On the other hand, I'm in favor of higher taxes than income on short-term capital gains, to encourage investors to focus on long-term gains rather than short-term extractive exploitation of assets. I favor lower rates than income tax on long term gains, say assets held for five years.