Uncertainty about Taxes
Republicans and businessmen complain about uncertainty for planning, but a lot of that is due to the fact that businessmen are lobbying for change, and Republicans want to give them lower taxes. Meanwhile they block major changes to the tax code that might increase some sort of taxes. The Republicans have problems because they have so many special interests to take care of, from defense contractors to oil companies, to neighborhood businesses. Something that helps one, might harm another. So, they are responsible for much of the uncertainty that they complain about.