I asked the Toyota folks that same question when we picked up our car last week. He said, No, because of the exceptionally tight tolerances these days, most new cars (he means Toyotas, no doubt) don't need a tedious break-in period.

Of course, that's pretty much the answer you'd expect from a salesman. We're still taking it a bit easy. A related thing he said did resonate for me: that your FE on the gas engine will improve somewhat over time when everything settles in.