"there is no evidence that Tamiflu would be of any use against a human form of H51."
Yes there is. It has been effective against most (but not all) forms of the bird form of H51. Any human form of H51 will more likely than not come from the majority of strains of H51 that have been effectively treated by Tamiflu. And yes, there's a chance the mutation will cause Tamiflu to lose effectiveness, but there's also a very good chance that it won't.
Do you think all these nations all over the world are frantically stocking up on Tamiflu because they know it won't work?
It does appear that current H5N1 strains might require a higher/longer dose. Worth keeping in mind if anyone is planning a purchase (better be a real quick purchase).
An Article in this months Scientific American backs up Tamiflus effectiveness, but it takes high dosages...still works though.