The Tax Policy Center, a joint venture of the Brookings institute and the Urban Institute, both viewed as left center reports that Cain's 9-9-9 plan concludes that more than 90% of people earning $37,090 (the bottom 40%) would see a tax increase. And that those earning less than $17,900 (bottom 20%) would pay $1854 more in taxes by contrast the top 20% with incomes greater than $111,000 would set their taxes cut by $14,400

This has strengthened fiscal conervatives view of Cain's plan because close to half of U.S. taxpayers, mostly lower and middle incomes households do not pay taxes under the current tax plan. The top 20% would bear 51% of the burden under the Cain plan down 17% while the bottom 20% would bear 3.4% up from 1%

(WSJ "Study Puts Cain's Tax Plan Under Microscope" pageA5)

I believe that as it stands now retirees will be faced with a double taxation because they will be spending income that has already been taxed and/or will be taxed when withdrawn from IRA's, etc. I am also believe with the passage of the time the consumption tax will continue to rise well into double digits.
But even now taxpayers will be forced to pay a state tax plus the federal consumption tax in florida that would be 16%.

Because of this and numerous other reasons this lan will never see the light of day