Brother I bought a Nissan AD Van 2007 model in Sept 2012. Frankly i would recommend it whole heartily to anyone looking for a new car.
The car is performing like a charm, noiseless engine, no vibrations and beautiful handling.
Its performance on Petrol for me is 13 KM/liter (with AC) inside the city ... i must remind you that i am in Lahore and my main route for travel is Ferozepur Road (which is screwed up due to the BRT project construction) meaning i drive alot in heavy traffic in slow speed and get stuck in traffic jams too.
Where as on long route its performance is about 17 Km/liter. I checked this mileage when i drove from Lahore to Muzafarabad and back to Lahore. It handled like a charm in the mountain area as well.
Not to mention the space the car gives you, you can move half a house in this car.
Only slightly negative thing are the rear seats of the AD Van which are not very comfortable. But these seats can be changed with more cozy seats or one can simply get a good seat wala to add cushioning to the existing car and give them the sofa look.
As for CNG, frankly my car does not have it installed nor do i recommend anyone to go to CNG specially considering the present gas situation in Pakistan.