The real question of any tax reform should be what is taxable, not what's the tax rate.
Would every purchase really be taxable under this "fair tax"? Would a single mother on welfare have to pay 23% sales tax on baby formula? Would you have to pay sales tax on the purchase of your primary residence? The Fair Tax people say yes, but you can see how easy it would be to start saying this or that should be exempt from sales tax. And even in the current form, the tax would exempt purchases for resale and the sale of used items.