Dissociatives and their use for exploring the mind.

This seems to be a fairly hot debate amongst psychonauts that I have met and conversed with. I for one love the concept of entering a space of blankness occupied only by the mind. I am currently experimenting with the new ketamine analogue MXE, and it has brought back my love for these substances.

Now, Alex Shulgin has said that dissociatives have no use as psychotherapeutic drugs, but I tend to disagree. One of the main uses for ketamine as a therapeutic drug is to help with phantom limbs. While this doesn't have much to do with being a psychonaut, I figured that I'd include it.

So, what do you all think of dissociatives? Are they mind killing chemicals that should be destroyed, or do they have an innate purpose in the exploration of the mind?

EDIT: I am also very interested in those of us that are normal users of dissociatives! How has long term use effected you? Would you say that it is worth while? Also, why are dissociatives some of the least used drugs in the US?