While I would love something in a smaller size, I agree that it would be a real pain to completely change over. Most of the time I am just fine with the size of my cameras, but there are a few times when just out and about smaller would be better.
As much as there has been others that have complained about the IQ of the original 100-400, my copy seems to be quite sharp. I have used the 1.4 TC with taped contacts, but that is a real pain. The slow auto-focus has frustrated me a lot of times too. As far as the push-pull goes, I quite like it, or at least am very used to it.
$200 for 10 days does not seem too bad, though for 2 weeks, and in Canadian Pesos, that might be fairly costly. Worst case, I will just take the 5D II, and it will do good, as it always has. For video, I have considered getting a small dedicated video camera too. That would be much cheaper than upgrading, that's for sure. 