I just bought a Alto Lx. Its small & cute car with all advantages keeping in mind like nice looks, good power, low maintanance & best of all is its fuel economy. I am sure it gives approximate 20-25% savings on fuel when compared to other cars. Any other same segment car would possibly give you best of 17 KM/Ltr while this car easily gives 21 KM/Ltr & I am sure in a long run it saves a lot.
Most of it, I feel I am doing my best towards reducing environmental hazard by driving a car which consumes lesser fuel & thus lower per capita emission. All & all, its a recommended vehicle.
It does get a beating while driving in crowded or cramped places as absence of power steering pinches during such times. But while driving constant on a highway it does not make much of a difference.
Happy driving!