Pro: Scandals overtaking the IRS are an indication of an out-of-control bureaucracy. The founders believed that levying direct taxes would be a threat to liberty. They therefore strictly limited such taxes. The 16th Amendment was necessary to implement the income tax. The result of this was the creation of a bureaucracy too big to control.
The behavior of the IRS is disaster for representative government and free elections. The IRS attacked the grass-roots groups but let the super PACs run amok. The founders were right: Repeal the 16th Amendment or face tyranny!
Con: To repeal the 16th Amendment is to strip the majority of power from Congress. Its members will never surrender the power to give favors to one special interest group or another and to persecute those who are a threat to their agenda.
A national sales tax would encourage people to save money, but this will never fly because business and the economy demand the consumption of every dime you have. The thought that you might save money instead of barrowing it and paying outlandish interest is more then the folks at any of the credit card companies could permit. You are the minion of this government and they want to keep you as their slave.