My Mazda5 didn't get the advertised mileage either, but the mileage was still decent. After mine was totaled last year, I considered getting another one, but decided against it because finding a good used one was difficult and I found out they discontinued the model in the US. I was worried that that would make finding parts more difficult.
We had a 2007 model, and there was a major issue/defect with oil injector (not sure the correct term). It was a $700 fix and there were no aftermarket parts. This was a widespread problem with the earlier models of the car, but I think it was fixed with newer versions. Of course, the car was totalled three months after we made the repair. 😬