If Plane Shift can land you above solid surfaces than the spell cannot be used to take you back to the material since odds are it will land you so high up gravity will not pull you toward the surface at any relevant speed.
It also goes to efreeti and janni, so figuring out how useful it is now will be valuable in the future.Is it useful? Yes. Gamebreaking or overpowered? Not really - not at the level it is available. Remember, the standard Djinni has an LA of +2 right now, on top of 7 RHD for an ECL of 9. Teleport is a thing.
Basically, you're trading a bunch of time, a lot of Knowledge(Geography) checks, and numerous potentially hazardous situations, to save a casting or a scroll of Teleport. Or, in other words, not enough to really matter.