I have had almost continual leakage problems with my AirLift 1000s. The hose is always getting a little kinked coming out of the bag, and then it leaks. I have tried various things, including putting another, protective hose around the area were it kinks.
When they work, they do a nice job. My tongue weight is right around 650, and it keeps things up. I do have a weight distribution hitch which does most of the leveling, but that last 1" needs the air bags. With the bags, my headlights are just a little high, and blinds oncoming traffic.