Since they are nocturnal, leopard geckos have poor vision in bright light. Their hearing is more in the form of vibrations, but they do recogonize voices! (mine all come out when they hear me talk).
I had a sneezing fit last night when we were feeding the babies. One of them wasn't very happy about the sneezing and starting screaming at me. Pissy little thing, though it was amusing.
I had a gecko who came when she was called, too. And actually, if you didn't tell her you were going to touch her before you did she's scream and occasionally try to bite. So I always had to say 'I'm gonna pick you up' or 'I'm gonna pet your chin' etc. before I did... And their vision is pretty good, you can tell when they see food. One of mine now, though, is almost totally if not totally blind, and it's pretty easy to tell, especially when she eats.
From the different items I've read their vision is descent although they aren't 20/20 by any means. Their hearing is descent as well; but as Marcia said it is based on vibration.
Their most powerful sense is smell and taste - with their Jacobson's organ they can taste air that they pull in through their nose. Just like a snake would. Thats why they warm up to you over time because they begin to know your taste and smell.
I'm not trying to be a smart ass but isn't all hearing based on vibrations?
Maybe Marcia meant they sense sound with a different part of their body much like a fish and their lateral line?
I find my geckos are very sensitive to sound. If I pull out a tub and simply whisper something to let the gecko know I'm there I'll sometimes see them flinch as they become startled by the sound of my voice.