I am owning a Maruti Omni 8 seater LPG for the past 2 n half months and I am satisfied with its performance. As I live in hilly country with bad roads(Nilgiris District, Tamil Nadu) the Omno 8 seater LPG has stood in good stead. No question of going too fast, we rarely go faster than 60 kms - hilly driving with curves limits your speed. With only two people going in it going up steep slopes is also not that problematic. Of course we switch to petrol, in steep inclines, but gas also performs well. Not taxing the engine too much: only for short stretches.
After 2, 000 kms the pick up was less: the filter was choked with debris. Had it cleaned and it is okay now. Petrol efficiency is low - less than 10 kms per litre. About the question of stability, well, we do not drive that fast, so no problem there till now. All highways in hills limit your speed.