They probably have some faults, but the general conclusions smell right to me: I don't think they're in the "really screwed up and wildly misleading" category, but in the "ok, interesting, could use some work though" category.
EDIT: I should probably mention I work at Rackspace, and thus everything I say on this subject should be taken with appropriate grains of sand :)
Many argue that the AWS ecosystem (25 services at last count) and the extensive featureset of AWS outweigh the bare bones "fast" metrics of other providers.
I think like the poster above is mentioning...there is generally more to it than a simple metric or two sampled a few times from a single endpoint. But I guess it all lies on ones definition of what they consider valuable...