The desire for jacking in, taking dex, simstims, microsofts and the like can be seen as a desire for self-exploration, and perhaps a method for self-actualization. The lengths to which people go in Neuromancer to stimulate themselves and reinvigorate their reality are incredible, and it seems much of the technological advance that Gibson describes falls into two categories: extending life, or making it more interesting. The first is obvious; there are constant operations and transplants going on through the novel, Case being the prime example. One can go on and on about being a cyborg in Neuromancer and the technology involved.
However, the second is more interesting to me, but less talked about. Case seems to me a futuristic Timothy Leary, somebody who's looking to expand his mind with all the means he can find. The technologies that Case is best at - the matrix, simstim, etc. - are involved in entering alternative consciousnesses, to the point that he abandons one self for the other self with ease and delight. During the break-in to capture the construct, Case spends hours on end jacked in and forgets to eat, doesn't bother showering or having breakfast when he wakes, and just generally immerses himself completely in this expansive project. His entrance into Molly's head is an exhilarating experience for him. And when his ability to enter into the matrix had been taken from him, he abuses dex to return to some other states of consciousness that he remembers the matrix bringing him (he'd forgotten what "real fear" felt like).
I can go on and on about what I think this implies, and all the issues it touches on, but here's at least a quick summary:
The point: I think it's fascinating to see what the psychology of the characters in escaping into cyberspace tells us about what they are escaping from. Jaron Lanier talks about the simulation of virtual reality as somewhere where we can create all those dreams that we could never communicate, and have other human beings experience totally what we experience; it's "cuttlefish envy". Well, maybe Case is doing just that, having become disillusioned with what one reality can offer, seeks to make that connection with himself and others - namely Molly - through the virtual spaces he can.