Took delivery of my new Sonata Hybrid on July 18.
Very happy with car so far.
Five tankfuls of fuel have given me an average over 39 MPG...if the tank is mostly highway driving I get average over 40, if mostly city/errands and such about 36.
No problem with switching between electric and gas engine. I think there may be a learning curve to learning to drive the car for the most economy as sometimes the gas engine will come in pretty strongly, especially in hilly terrain.
Car is very comfortable for long drives, my bulged discs don't even know! (to be fair, my '07 Sonata was the same way).
The handling may not be quite as good as my last Sonata, but this one also feels much bigger.