The thing that keeps coming back on the FairTax is how complicated it really is (see here); besides that, there's no reason that the FairTax couldn't be transformed over time into a monster worse than our current system; imagine, if you will a FairTax which varies the rate of the sales-tax based on your income (ostensibly to keep it from being "regressive") and then adding the type of item to the set of variables (oh, look ammo now has a 5000% tax!)… now imagine that system tied into commerce itself, say by forbidding buying or selling to anyone who isn't registered in this commerce/tax system (ostensibly to prevent fraud/tax-evasion; don't worry it's perfectly secure, by RF-microchip embedded in your forehead or right hand).
In short, the estimated savings in terms of combined yearly compliance/economic opportunity costs of the tax code is about 75%, not the 95% you get under FairTax.
I seriously doubt that 95% number.
My biggest problem with the Fair Tax is that it subjects post-tax income to new purchases (and therefore subject to the Fair Tax).
That means that I would have paid income tax on that money when I earned it under the current system, and then I’d pay the Fair Tax (the replacement for the current tax system) again upon buying something under the new tax system.