As of January 1, 2010, the IRS has removed the income restrictions on Roth IRA conversions. Since withdrawals from Roth IRAs are exempt from income tax provided that you're at least 59 1/2 and have had the account for at least five years, converting your traditional IRAs to Roth IRAs may make sense for you. Plus, Roth IRAs have no required minimum distribution once you reach age 70 1/2.

The plans that can be converted into a Roth IRA include traditional IRA, SEP IRA, SIMPLE IRA and some qualified retirement plans such as 401(k) and 403(b).
 
There is an incentive in 2010 to make the conversion. Everyone who converts this year may defer the income recognition from the conversion to half in 2011 and the other half in 2012. So you can start earning tax exempt income in 2010 and not have to pay the tax bill until you pay your 2011 and 2012 taxes.
 
To benefit from the conversion you need to be young enough to enable the Roth IRA to grow large enough to cover the taxes that have to be paid on the conversion. Ideally, to get the best benefit from the conversion, you should pay the taxes from non-IRA funds. Depending on the balances in your IRA accounts, it's not always easy to come up with that much non-IRA funds to pay the taxes due on the conversion; however you don't have to convert all at once.
 
It's not right for everyone and there are several considerations or other matters. For example, if you will be in a lower income tax bracket when you retire than you are now, the conversion may not be to your benefit.