Two additional factors of consideration:
1. You do not have to pay tax from traditional IRA balance when converting. You can use OUTSIDE money. Effectively this works like ADDITIONAL contribution quota for ROTH IRA. If you have already maxed out ROTH IRA contribution, or do not qualify due to income limit, this can represent a large benefit.
2. Do you trust government not raising your tax rate? With the federal deficit and incoming higher interest rate on government bonds, I will not bet on that.
I agree with gradually converting into ROTH so you do not bump your marginal tax bracket. Also if you can convert when you qualify as a resident of a state with zero-income tax rate, it is even sweeter.
