I am an owner of a 1400 cc GLG Xeta and have driven more than 5000 kms.Its a really good car.I havent really faced any problem with the performance of the car.it has consistently given a mileage of 11-14 km/lt with ac on depending on the road conditions.
However, the engine technology isnt so good.It makes more noise than other cars with similar engine capacity.Guess thats the price of the car!!.Hopefully, the TATAs will make more refined petrol engines in future.
Some people might be facing problems with the ac.I suggest to get the ac comp. belts checked for tightness/alignment.
The car can easily speed upto 100-120 kmph.It does take some time to further increase the speed.Howevr, I have driven the car at 152 kmph on the Baroda-Ahmedabad expressway.It really feels fast.....and I feel that the car is balanced too!!!.
The brakes arent so precise like that of the Marutis or the Hondas.....so be careful when driving at high speeds!!!.
Cheers and happy driving!!!