A couple of examples of the more cheerful variety:
There were people, in the 1960s, who became briefly involved in Scientology, during the days of the old Grade Chart, and went up to Power Processing, were happy with the results, and then left, never to return. IIRC, there was a steady flow of Swedes who went to St. Hill for Power Processing (the Grade after Grade 4 and before "R6 End Words" which was before the Clearing Course). They did their Power Processing, were happy, said goodbye, and never had anything to do with Scientology after that.
They definitely knew something that we didn't.
I recall one young woman from the 1970s, from Puerto Rico. She spoke English poorly and was extremely shy. She came to the "Org" and did the Comm Course, and a few other courses, then the Student Hat, and she improved, and she became extroverted, and her English improved, and then she did something I didn't understand at the time: She quit Scientology, went back to Puerto Rico, and had nothing further to do with Scientology.
There were others who did the same sort of thing. Dipped their toes in Scientology, got something out of it, then got the heck away from it.
All the Scientologists thought they were foolish and were missing out, etc. Some thought they must have hidden crimes, or at least lots of misunderstood words.
Ah! But these folks who got away from Scientology were
so wise.
Comm Courses were known for this. People would do them, have a good time, have "VGIs," and then leave.
The most notable Comm Course story, of which I know, is a fellow who did the just released "Hard TRs Course" in the early 1970s. This person regarded the Comm Course (briefly, then, also the "Hard TRs Course") as an inexpensive means of therapy for his wife (it cost, I think, 35 dollars) and a kind of odd head-trip for himself.
It took about a month, and I think his wife benefited - was more emotionally stable - and he seemed to get a kick out of it too.
This person had the wisdom to recognize that this was probably as good as Scientology was going to get - especially judging by money-spent/potential benefit ratio - and firmly rejected any future involvement with Scientology afterwards.
He ensured this future non-involvement in a novel manner, when he wrote his "Success Story" at the end of the course, describing how (to paraphrase) "Now that I've completed the TRs Course, I'm going to become a leader in the Hare Krishna movement."
He was labelled a "squirrel" and shown the door, and that ended his and his wife's involvement with Scientology.
A wise man.