Now, one more thing I found on these conversions- you may be able to "re-characterize" your newly converted Roth IRA back to traditional within the year after the original conversion.
Why to do that?
Suppose you had $10,000 in your traditional IRA, which you funded tax-free. Upon conversion, you'll owe your going rate (28-32% or whatever your tax bracket is) on this converted amount.
Suppose now, that within a year your original 10k dropped in value to 8k. Then you can do "re-characterization" of your Roth back into traditional IRA to avoid paying taxes on already depreciated asset.
Some authors even advise to create several Roth IRA's and transfer each kind of assets
( US large, US small, emerging markets, bonds, etc) into a separate Roth IRA. That way, you can see what depreciates ( hopefully none, but you never know), and "re-characterize" it, leaving appreciated assets in their respective Roths.