401(k)->roth ira

Anytime you convert pre-tax retirement dollars to post-tax retirement dollars, you have to pay the tax, so the answer to your question is "no". You "need to pay taxes for the conversion like you do regular to Roth Conversions."

All true, but I'd add - A conversion to an IRA, then to Roth leaves the door open for recharacterization. If when doing your taxes next year you see your conversion put you just into the next bracket, you have a chance to back off the exact amount, and then convert next year.

This is an excellent point as in-plan Roth conversions can not be undone. Another thing to watch out for is NUA (net unrealized appreciation). If your employer plan holds highly appreciated employer stock, you would the lose the capital gain benefit of NUA if you transfer that stock to any type of IRA. And... lastly, in-plan Roth conversions are still very new (ATRA 2012) and most employer plans have not been modified to include a Roth feature and allow for conversions.

You have to convert in pieces. In 2012 the standard deduction and exemption is 5950+3800—50. If you have no other income, then you can convert $9750 tax-free. If your only other income is social security, then you still may be able to convert $9750. I did a calculation that showed if you have 30k of social security in addition to the $9750 of conversion income, then none of it is taxable, but if you have 36k then some of your social security is taxable, and so you would have to convert less than $9750.

Now if you are over 65, married, have itemized deductions then you can convert even more.

All the same, it's good to convert to traditional IRA first, then convert in pieces so that you can recharacterize/undo part of the conversion. The other post mentioned this.