I've never seen a dispatcher's note on the flight plan that said, "I planned you at M.76 because you have a 150kt tailwind."

On the 777 we use pretty much the same cost index all the time, which usually results in a cruise of around M.825, headwind, tail wind, or no wind. (the FMC will go a little faster into the wind, a little less with tail, but not much) The only problem is, Customs in ATL doesn't open until 05:30, so they won't let you open a door, or even park, until 05:30...so if you get in earlier than that, you sit on the ramp with an engine running.