It is necessary to separate reasonable extrapolations and speculation about mind uploading from the magical thinking surrounding it. The first major question over the plausibility of mind uploading is whether consciousness is computable in its entirety (or in other words, is the "strong AI" view justified?). This question, of course, remains unanswered, though considering the current state of cognitive science and brain-computer interface technology, it is not unreasonable to think that consciousness will be found to be computable in the future.
The second question is a philosophical one, and that's where things get a bit murkier. Besides predictions that mind uploading technology will be on the shelves of a store near you in the next few years, the least plausible prediction about mind uploading is that it is a means of somehow achieving immortality (or at least close to it). This would require some form of dualism to be true, i.e., that "you" or your identity can be "uploaded" to a computer. If mind uploading technology were achieved, it's more likely that it would simply create a computerized facsimile of your conscious functions. The philosophical problem with uploading "yourself" to a computer is very similar to the "swamp man" thought experiment in which a clone is made of a man while the "original" is killed. Just replace "clone" with "uploaded mind." This is one reason that has led critics to say it's not at all clear that the concept of an uploadable mind is even meaningful.
 See also
- Collection of articles on mind uploading
- Welcome to Life - The Singularity, Ruined by Lawyers.
- Against Naive Uploadism: Memory, Consciousness, and Synaptic Homeostasis, Seth Weisberg, H+ Magazine
- Why Transhumanism Won't Work, The New Atlantis (A misleading title, the article is about mind uploading, not transhumanism in general)