Down side is they cost as much as a GT Mustang. They can't hang with the Mustang. I realize performance is not the end all for some folks, but on a performance vehicle the raw numbers are all that matters to me. As to this EcoBoost engine, I have one now and have had others...you can be Eco or Boost but not both. You start mashing that baby you are looking in the "teens" for mileage. But again, who cares on a performance car? That's what you get them for. The ONLY downside to this car is the entry fee, compared to other cars of like performance.