The two year tax extension...

...does not solve the uncertainty issue. If you are a business looking to make an investment in a new project, you don’t care what tax rates are in the next two years, you care what they are for the next 10 years.

Not only that, a business person probably cares less about tax rates in the early years, because a new project usually involves upfront costs, such as hiring and training new employees or purchasing new equipment, and those costs can usually be deducted either immediately or during the first few years. The profits, if they come at all, come in the out years.