Some of the possible benefits to mind uploading would be: the ability to completely modify your surroundings (thus experiencing things essentially first-hand that would be utterly impossible otherwise); the ability to escape the
dangers of biological life (there could easily be tremendous safeguards against 'hacking' or any such); the ability to effectively
compress time by modifying your own
clock speed (thus making minutes seem like days if you had the
computing power/speed); and access to assorted other amazing ways in which you could
alter or improve your experiences.
However, a problem I've found with the idea of mind uploading, or of most other forms of
ego transfer (such as
Other Memory and
gholas from the
Dune series), is the lack of
continuity.
That is to say, it's hypothetically very possible to
emulate the functions of the human brain so perfectly that some exact copy of a person's
thought processes (memories, emotions, etcetera) could be created perfectly. And that copy would, in effect, be the person who it was modelled on. But the person would not be the copy--she would still feel exactly the same, except she'd be aware of (and able to interact with) a
digital version of herself.
Which is really an
interesting idea, and all, but it doesn't effectively provide anything more than a very abstract form of
immortality. The
biological human would still
grow old and die; would not have access to all the amazing capabilities of her
digital self; would effectively gain very little
concrete benefit from it aside from the simple knowledge that someone exactly like her was being given an
amazing experience.
Of course, this isn't an
insurmountable obstacle. Given the level of technology necessarily involved, for instance, it wouldn't be too difficult to imagine simply implementing some form of
MMI (or
BMI, pick your acronym), and then moving the still-active thought processes from the brain to the computer, such that continuity is maintained and the digital version of the person is, in reality, the same
consciousness as the biological person. Or a subject could gradually have her entire brain replaced with
cybernetic implants that maintained the exact function and state of their biological counterparts (to avoid memory or
identity loss) and then once her brain was entirely digital, transfer her consciousness into a
computer system that way. Of course, whether or not a consciousness could remain the same during such a transfer is rather unclear.
But then, this is all
hypothetical anyway.