well i have a vti orial prosmatic late 2005. it runs perfectly on CNG. also this is my first automatic and I can tell you its a really joy driving an automatic. i feel relaxed and fresh even after driving all day in city or going to murree/bhurban,etc .no manual frequent clutch pressing/ changing gears !!
also the myth that automatic changes gear at high is not true. it depends on how much force you put on pedal. the harder you push , the higher the rpm at which the gear will change.