I think if someone is not prepared to experience their waking hours as less
real than they expected or want to believe, then it can be a scary experience. I have experienced derealization as a result of depression and anxiety disorders, and it was a terrifying experience to think of everything as just a dream, even the people I knew and loved. Everything felt very empty and meaningless; It was a very lonely experience. But, it passed and I started living in a world that wasn't just my own dream. Mainly I think it was a bit of a misconception on my part that everything being dreamlike, or a mental projection on my part, does not mean that people are a figment of my imagination, only what I see them as or who I think they are, is a projection of my mind, but I am not alone.
Now, I experience what could be called depersonalization, but it is not from any mood disorders but through deliberate dropping of self identification with the body and hightened awareness of the present situation; thus, it is not a scary experience and is actually quite calm and peaceful.
Though I experience things as being less
real in the common sense of the word, things do appear to be
more real than they used to, in the sense that things are more vivid, though it is more understood that there is a dream-like nature to the appearance of all objects of perception.
Also, the very gradual, calm transition of perception based in personal conviction in the nature of things makes it easier to handle, rather than being very depressed and anxious and worrying about things being real or not because you are afraid of losing things you love
So, there is a bit of a difference between the derealization or depersonalization that are symptoms of other mood disorders (which they usually are, they dont usually come about without depression or another disorder being present already) and the derealization or depersonalization that is the result of a spiritual emergency. But, I think the main difference may be in approach and the state of the individual prior to the inception of derealization/depersonalization. I think if I had a mentor to help me handle my problems in the first place, then it would have been a different situation.
EDIT: I would also add that, in the situation where derealization/depersonalization is a symptom of another psychological disorder, usually a mood disorder, then it is believed to come about as a result of, 1) the brain slowing down sensory and mental processes to handle the overflow of anxiety and problems, thus things seem unreal (derealization), and 2) disassociation (whether willful or inadvertent) as a result of trying to separate oneself from the anxiety or problems (depersonalization). And then of course, it could be a completely different situation and neither of these situations apply
So yeah, I guess you could say the Matrix portrays this.