Well, there can be a question of what rate of disposition change is consistent with being still the same person. About telling apart - well if someone cannot tell a computer program and animal apart, they have a trouble.
It looks like currently humanity can learn a lot about concept of self but seems to be a bit afraid to try by medically temporarily freezing inter-hemisphere link... What would the person remember as "past self" after re-merging?
All this is moot anyway because gradual uploads are as likely to be possible as stop-and-go ones.
A new paper has gone up in the November 2011 JET: "Ray Kurzweil and Uploading: Just Say No!" (videos) by Nick Agar (Wikipedia); abstract:
The argument is a variant of Pascal's wager he calls Searle's wager. As far as I can tell, the paper contains mostly ideas he has already written on in his book; from Michael Hauskeller's review of Agar's Humanity's End: Why We Should Reject Radical Enhancement
John Danaher (User:JohnD) examines the wager, as expressed in the book, further in 2 blog posts:
After laying out what seems to be Agar's argument, Danaher constructs the game-theoretic tree and continues the criticism above:
One point is worth noting: the asymmetry of uploading with cryonics is deliberate. There is nothing in cryonics which renders it different from Searle's wager with 'destructive uploading', because one can always commit suicide and then be cryopreserved (symmetrical with committing suicide and then being destructively scanned / committing suicide by being destructively scanned). The asymmetry exists as a matter of policy: the cryonics organizations refuse to take suicides.
Overall, I agree with the 2 quoted people; there is a small intrinsic philosophical risk to uploading as well as the obvious practical risk that it won't work, and this means uploading does not strictly dominate life-extension or other actions. But this is not a controversial point and has already in practice been embraced by cryonicists in their analogous way (and we can expect any uploading to be either non-destructive or post-mortem), and to the extent that Agar thinks that this is a large or overwhelming disadvantage for uploading ("It is unlikely to be rational to make an electronic copy of yourself and destroy your original biological brain and body."), he is incorrect.