My understanding is that calendar year 2010 is the first time there are no restrictions on converting an IRA to a Roth IRA.
In short, whatever amount converted is treated as regular income for tax year 2010 so you have to pay tax on it but then it can grow tax free forever.
Do you think the authorities could change the rules and tax it again later?
If one believes tax rates will be higher in the future, isn't conversion now a no-brainer?