The 1040EZ will probably be used by about 25 million taxpayers this year—about one in six. The EZ has just 12 numbered lines and you can't file supplementary forms.
Before you become too enamored of all that simplicity, consider the restrictions that put the EZ out of reach of most taxpayers. Although the EZ is open to both married and single taxpayers, it's available only if you don't itemize deductions, have no dependents and your taxable income is under $100,000. You can't use the form if you have any income from dividends or capital gains, self-employment, taxable social security benefits, a pension, alimony, more than $1,500 in interest, deduction for educator expenses, student loan interest deduction, tuition and fees deduction, education credit, retirement savings contributions credit, or health insurance credit for eligible recipients.