I find the Alto a good small segment car. It is definitely better than 800 and the price difference is certainly a worth investment. The gear box is better than 800 and so are the noise, temperature and vibration insulation. This car has more head room than even Zen. The overall feel in the car is much better than 800. If you want a luxury car, then Alto may not stand up to your expectations.
The things that I found odd about the car are the headlights. The headlight cover is made of plastic and you cant go for a brighter halogen lamp without risking it to be broken by heat. Just to make matters worse, the Alto doesnot even have a place in the front bumper to include an extra lamp.
As far as taking rough is considered, I stay in Bangalore and every time I drive, its like driving on a rough terrain. My vehicle has easily survived me for 15 months now without a complaint. Whats even better is, this car doesnt have a carbuerettor and the maintenence required is really low.
So overall I rate this car as a good value for money small segment car.