What's your current estimate (or probability distribution) for how much computational power would be needed to run the C. elegans simulation?

I think the simulation environment should run in real-time on a laptop. If we're lucky, it might run in real-time on an iPhone. If we're unlucky, it might run in real-time on a cluster of a few servers. In any case, I expect the graphics and physics to require much (>5x) more computational power than the C. elegans mind itself (though of course the content of the mind-code will be much more interesting and difficult to create).

Once your project succeeds, can we derive an upper bound for a human upload just by multiplying by the ratio of neurons and/or synapses, or would that not be valid because human neurons are much more complicated, or for some other reason?

Unfortunately, C. elegans is different enough from humans in so many different ways that everyone who currently says that uploading is hard would be able to tweak their arguments slightly to adapt to my success. Penrose and Hammeroff can say that only mammal brains do quantum computation. Sejnowski can say that synaptic vesicle release is important only in vertebrates. PZ Myers can say "you haven't modeled learning or development and you had the benefit of a connectome, and worm neurons don't even have spikes; this is cute, but would never scale."

That said, if you're already inclined to agree with my point of view--essentially, that uploading is not that hard--then my success in creating the first upload would certainly make my point of view that much more credible, and it would supply hard data which I would claim can be extrapolated to an upper bound for humans, at least within an order of magnitude or two.