Hi WRC, my plan has been to use a roth conversion ladder for the IRAs while living off the dividends from taxable accounts, pulling however much I can to minimize taxes while keeping myself out of the Medicaid gap. I probably won't convert the 401k right away because it's a solo-401k that my wife funds through her internet work (a business writer)--but we may start contributing to a Roth 401k instead going forward, unless we need that income.
My thought has been to save the 457 for last since it's so flexible with RE to withdrawals. I can always withdraw it penalty free in a year if something unexpected comes up that I can't fund from my regular investment accounts. I'd prefer not to have to, but it's certainly better than having to pull money out of a real IRA early. We've about 25% of our NW in the 457, so there's quite a few years of savings in there if it came down to it. I haven't considered the 457 in relation to social security at all. Do they conflict in some way? SS is so far off it hasn't played much into my planning, except insofar as it's 'free' life insurance for the wife and kids if I die early.
My thoughts on the conversion ladder were the same as yours, but now that we're getting closer I'm not sure we're going to have as many years of true/near zero income to convert as I had thought. I'll probably end up having to pay SOME taxes at least on the conversions, but hopefully not much.