I bought this car last year and its nearly 5 months. I have completed close to 11K kms in 5 months. For the price you pay it is the best in its class. Drive is smooth and comfortable. The only drawback I have seen is that the steering is bit hard and grear shifting not as smooth.
In January I drove it to my native in AP from Chennai, its 600+ kms one way and I easily made it in less than 7 hrs. After driving the car for 7 hrs I felt like drving from my office to home which is only 20 kms in city traffic.
I easily crossed 160 kms/hr and it felt like I was drving the car at 60 or 70. Breaking is execellent and you can depend on it.
In city I get 13.5 km to a liter and on Hwy it depends on the speed you drive. On my onward long journey I was constantly crossing 150 and the mileage was an mere 13, on my return wanted to check the mileage and by great difficulty maintained 100 and got a decent mileage of 16. If you can maintain you speed at around 70 then I think you can get a even better mileage.
But I can bet it is not easy to maintain a speed of 70 on a hwy when the roads are empty, without you knowing the car would be easily crusing at 120+.I would recomed this car to a person who has a budget of around 10 L and would like to go for a Diesel car.
Sundaram Motors service is changing a lot and my experience with them is good. Spares are not expensive when compared to Skoda and other makes in this class.
19-aug-2008: Its close to an year and I have clocked 16 K + kms on Magnum. With some sensible driving I am able to get an constant 14+ kms in city driving. The point I make sure is not to cross the 2K rpm mark (when the turbo kicks in) in city driving. No major issues till date.
Gear shifting is much smoother now.