usable third row, compact vehicle, good fuel economy - the Mazda5 is really the only choice. I could barely fit in the Rondo's third row.
That's not saying the 5's third row is as comfortable as a minivan's or a full size SUV (although I find it surprisingly better than some full size SUV's), but that's what you'd expect with a much larger vehicle.
My in-laws have a Pacifica. It's gigantic, yet the 5's third row is more comfortable. It's criminal how Chrysler couldn't find more room in the Pacifica's third row.
We had an '04 MPV. Third row was pretty decent, bigger than the 5's, not as good as Chrysler or Odyssey, but those "mini"vans are bigger.
The bottom line is that the 5's third row is usable, although the second row passengers need to scoot up a little.