I'd better get this post out quick, before everyone forgets what it was like to do their taxes. Now is the best time to point out that a flat tax (one without a progressive rate structure in which lower income levels are taxed at lower rates) won't actually make your taxes any simpler.
What did you spend most of your time on as you did your taxes? If you're an investor, maybe you spent it on totalling up all your stock gains and losses. If you get lots of income from different sources, maybe you spent it getting your motley assembly of W-2s and 1099-whatevers together. If you apply for a bunch of deductions, maybe it was getting deduction-related paperwork together and figuring out whether to take your standard deduction or to itemize.
Chances are, it wasn't figuring out how to work the progressive rate structure. If you used some software program to do your taxes, this took you no time at all -- the computer did it all by itself. If you did your taxes by hand, it was pretty easy to use the tax table in the book the IRS gives you, wasn't it? Just look up your taxable income, and it tells you how much you owe. (I've done it both ways, and I've never had any trouble with the progressive bracket system.)
So if you want to make things easier for tax filers, there's no need to mess with the progressive rate structure.