I own an '08 MZ5. It's a brilliant little vehicle.
I average around 25MPG in about 60/40 in town driving. I've pulled as good at 32MPG on the highway. It won't keep up with the 270HP Honda/Toyota vans but it's more than peppy enough chugging around town. If you lock the auto-stick into 3rd gear it merges onto highways with little drama. 2 lane passing maneuvers are mostly to be avoided, the little 2.3L in there can only do so much. But I rarely ever find myself feeling like it needs more power. Want yes, need no.
Space behind the 2nd row (with the 3rd down) is almost cavernous for cars of this segment. It really is deceptive when you look at it. The 2nd row is very comfortable for 6' adults and I find the seat hight much better what is available in the 2nd row of many mid/full size SUV's.
The car turns on a dime and gives you change, and has very good road manners. Noise levels on the highway are very good in the front seats. Gets louder as you go back.
Headlights are excellent and HID's are available, but certainly not necessary except for the look of them.
Room behind the 2nd row is even comparable to a Fit. The Fit has to fold it's back seats down for the same space leaving no room for passengers to be equal. The fit gets better milage, but comparing a high end Fit to the entry level Mazda 5 and the Mazda blows it away in features, comfort, room, and safety. And they really aren't that much different price wise.
My only real complaints about the car are a fairly anemic stereo and limited room in the front seats. Going from a Sienna or Oddy to a Mazda front seat is pretty night and day. It simply doesn't have the leg or shoulder room that the full size vans have. But it takes up a fraction of the parking space as those two.
Give it a good look over. For a family with kids under 12 or so, it's a perfect option.