We've got a 2010 for my wife's DD. Love the thing.
It meets our needs of hauling kids (and so far-what ever else we need) and is still fun to drive. She was pushing for the CX-7, but after taking the 5 around and realizing that it drove like a car rather than a truck, she was sold.
The back seats are tight for adults but are still manageable for short trips.
There's a forum dedicated to them:
2006 ~ 2010 Mazda5 Forum
At 22,000 miles, we've had no issues yet - just the normal oil changes.
We've got this and a '09 Mazda3 - I can't say enough good things about either car.