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.