I have owned a Santro Xing XG myself for about 3 years now and have done more than 30, 000 kms. I feel proud about it.
I would like to share my experience with all of you...
Space -
The Santro is an ideal choice for people with an height about 6 ft. There is enough space on the inside for a family of 2+2, but if you were to squeeze in 3 persons on the back seat, it is difficult.
Max two suitcases is what you can accomodate in the trunk and that I feel is fair enough the car is more for within city use.
Handling -
The car handles really well. The only problem being that at sharp turns, it skids even at low speed. This is primarliy due to the height of the car, but if you are to ignore this, the rest is just too good. the engine is pretty response, but with five people loaded, it gives you a feeling that it could have done with some more CC power.
The gear box is a bit rusty. In eRLX version they seem to have fixed it. During the third year I had a problem with the clutch plate which was minor and was fixed. Other than that no issues with the car.
Fuel -
On city roads I usually get close to 13 kms with AC and on highways 15+. But do remember that this car is not build for long dirves. 3-4 hours drive is what you can expect this car to do without making you feel tired.
Over all a very good car and I would say the best in its segment.