I purchased this car in jan 2007 after some basic research on mileage, after sales service, resale etc. Was one of the early buyers of this little baby.

I will list the pros and cons of cute yet powerful Zen Estilo here:

Pros:

High fuel Efficiency, I got 22 km / l + on Bangalore Mysore Highway.
Tried and tested engine used in Wagon R with tuning done for better mileage and responsiveness
Car has good space in front for the driver
Interiors are good for this segment car
AC is amazing
Power steering is amazingly smooth.
Its very very easy to maneuver this car in city traffic
Inside the car its noiseless--no sound of engine running till you touch the Gear
Lot of Boot space in the back of the car
Good control on highways

Cons:

Car Body material is very light
Gear shaft rubs the thigh of the passenger sitting in front next to the driver
Maruti needs to come out with more colours.

Its nearing 1.5 year for me and the car hasnt troubled us at all.

I recommend this car for a small family. 4 adults and 1 kid can be seated comfortably of average built. Its a baby Innova for us.
JD Power Asia: Maruti Zen Estilo ranks highest in the compact segment.

Cheers,

Sanjeev