it works to get the surface sirt off but not the dirt in the cracks or that has been on there awhile. From not cleaning the seat regularly. It could work if you scrub for a long time and kinda hard but that wears out the leather quickly so I prefer to use a strong cleaning agent.
we had access to a steam cleaner when i worked in a detail shop. I always used a light duty all-purpose cleaner and the steam cleaner to clean the leather in the used cars that we where going to put on the lot. I dont know how many times the used car manager looked at the cars and said damn yall do some good work.
a medium bristle scrub bruch and some leathercleaner did wonders on my 2000 gt with tan leather, you can even use it on the door panels and they look almost new. just wipe it with a damp towel at the end.