The Prius is only a mid-size in EPA World. In the real world it's a large compact. The HSH/KOH mileage is available, but you need to work with the car to get it because a heavy foot doesn't combine well with an assist hybrid. For easy mileage in a mid-size the 2012 Camry Hybrid or the Ford Fusion Hybrid are better.
HSH gets 40 MPG highway with 2.4L ICE. Camry hybrid gets 39 MPG with 2.5L ICE. The new 2013 Fusion Hybrid supposed to get 44 MPG with 2.0L ICE but we'll have to wait for the official EPA figure.