Why? Use the money now and deny Washington its use for a year. put it in the bank or pay down a debt. It won't change your overall tax burden. If you owe taxes you'll just pay them on April 15th instead of early. If not you get to keep your money without giving Uncle Sam an interest free loan.
Not true. You have to pay a penalty if you owe too much at the end of the year.
http://www.irs.gov/taxtopics/tc306.html