I don't really have an empirical "test" for subjective consciousness beyond my own immediate, first-person experience of it. This may sound like a concession or even a defeat, but I think I'm allowed to posit that phenomena exist which we currently lack the empirical tools to investigate. "Currently" is the key word; as I said before, it is arrogant to assume consciousness will forever remain a mystery to scientific inquiry, just as it is arrogant to assume it must be a simple extension of existing theories.

I admit I have nothing beyond my own experience to validate the idea of subjective perception, and I have no evidence beyond intuition as to whether or not a machine can "experience" input the same way a brain can. However, I think I'm still entitled to believe that subjective experience is a real phenomena whose nature can and should be explained, and that our scientific understanding is presently inadequate for this task.

EDIT: I can understand the fear of relying on intuition. After all, it's the same thing that led us to believe that lightning came from the gods. But that doesn't mean that we should throw out the entire experience of perceiving lightning. Clearly lightning is a phenomena we experience, but we still don't understand how photons entering our eyes produce the subjective experience of blinding whiteness, or how vibrations from thunder translated into electrical signals by the ear result in the subjective experience of the sound itself. The information is in the brain, but we still don't know how information becomes experience. This doesn't mean we have to explain it via gods, but it does mean we still have something left to explain.