If the economy is going full tilt and everything looks fine on the national horizon, then the old 6 month rule probably applies.
But as we all know that is not the case now. I agree with the rest of the Piggs, 1+ year of mortgage payments after you are done with closing costs (even if that’s less than 20% down).
As for waiting…I probably would at this point simply because things seem so unsettled at the moment. I’d re-evaluate in 3-6 months to see how things look then. But Walter’s point is a good one – if I too had waited until I was perfectly comfortable, I would never have bought. Sometimes you just have to hold your breath, close your eyes, and do it.