... My own understanding of this stuff is probably only uniquely applicable to me and my comment about "opinions vary" was in response to UM's dismissal of the concept as "imagination".
Another perspective is to treat it ALL as 'artificially implanted data' and allow the individual to determine, should he choose to do so, what seems to be 'real for himself'.
And no, implants don't necessarily imply some grand intergalactic conspiracy of spiritually suppressive beings, although that was apparently hubbard's view. That was clearly hubbard's personal paranoiac tendencies talking.
An implant is really just a time that something that isn't real, true, or didn't happen has been picked up by an individual and treated as if it was fact. It is life experience as false data, whether intentionally implanted in an individual or not. For example: social conditioning, religious educations, & cultural adaptation all qualify as implant techs, although such are generally regarded as benign aspects of human social life. So also with less apparently benign activities as military boot camp, hazing, and the rpf. Frankly the normal living environment is rife with false data which others are actively engaged in promoting as 'real' or 'true' to greater or lesser degree and with a greater or lesser willingness to use force in achieving acceptance. Any of that can be viewed as "implant data on a gradient". Factor in the apparencies of past lives and inter-spiritual sharing and the role that implants might play may be seen as potentially significant.
Hubbard's upper level tech is basically just the idea of applying dianetics & scientology processing to run out such 'implants' on what appear to be individual entities, however that may be understood. Hubbard and the church went overboard in specifying the necessary truth of his interpretation of a single unifying narrative in all such human experiences. The truth is that the concept of entities, ubiquitous in human cultures, can be understood in a variety of ways, not all of which posit the existence of separate spiritual intelligences.
Note: one such alternative view that has been presented by Paul Adams: http://www.forum.exscn.net/showthread.php?10114-Paul-s-Body-Thetans&p=211951&viewfull=1#post211951
But the basic conception of an individual identifying and untangling any such considerations, conscious or not, which may be impacting his thoughts is not itself an unsound idea. And the practice of identifying the possible presence, recovering the specific content, and spotting the point of origin and agreement of any such implant events greatly reduces any effect which might be produced by the entrenched concepts or ideas continuing to manifest subconsciously in present time.
What actually matters is the disentangling of individual conceptions & considerations, not the specific model by which these are understood to operate.
Mark A. Baker