There are a lot of spiritual authors who use the word "ego," and I am not sure if all of them had Freud in mind when writing.
In any case, the term is more to refer to the sense of boundary between localized points of consciousness (monads?!) and the universe. If water had an ego, every drop would think itself separate from the ocean. The death of the ego, then, is the dissolution of that barrier between self and universe.
Ego is also a very important thing, and it's not something you want to STAY dead--it also serves as an alarm system, to defend that boundary and protect the unique expression of divine consciousness that is "you." The problems we see today all come from the ego taking the steering wheel, rather than chilling out in the passenger seat, and knowing when to say, "Hey! Look out!"
Trust is medicine... knowing when to surrender... having faith in what is beyond the ego boundary...
And gratitude... thanking the ego when it speaks up, in feelings of defensiveness, honoring its purpose... without becoming paranoid.
Terrorism is the perfect example of a product of ego run amok at a collective national level. (Without delving too deeply into left brain psychology

), the ego's purpose is to defend a unique identity and protect. But when defensiveness and fear take over, paranoid delusions and a lot of tragic, harmful, and unnecessary actions result.
The experience of ego death is so profoundly healing because it reaffirms the source of all life (including the unique existence defined by ego). It gives ego perspective. Ego needs perspective to function productively--otherwise it becomes destructive.
My rambles about ego...
I would have to interpret a hypothetical death of the superego as a death of the greater spiritual whole, beyond ego--which could mean a collapse of the entire universe itself, and also nothing at all, because in ego death, one realizes, there is no such thing as death, just dissolution and expansion. That could be borderline not making sense, though.
