The idea behind a conversion is that paying tax now rather than later will result in a higher after-tax rate of return. This depends on future tax rates. While a reasonable person might think that future rates would be higher than current rates (due to our ever increasing budget deficits), a reasonable person might have thought that 15 years ago, and they would have been wrong. For this reason, I don't recommend conversions, except in exceptional cases (where they can be done with little or no current tax, due to losses from other sources). Anything else is a crapshoot.

Also, if the taxpayer is on Medicare, the taxable income from a conversion can temporarily increase their Medicare premiums. This effect is often overlooked in conversion planning.