I like something like this footer (though I don't think this is a great one: page-specific wiki actions doesn't belong, and I don't get the "Reports" column). It clearly doesn't serve as main navigation. For me, it's the "where do I go next" collection of links for when I've read the page. I think it can improve usability, not hurt it.
As for SEO, I don't think the concern should be "do we show up high in the ranks?" but rather "does a query in a search engine take you to the most appropriate page?" I've long been frustrated by Google not being able to find good answers to my Haskell-related questions. If there's anything we can do to improve this issue by changing the page layout and structure of
haskell.org, then I'm all for it. This in itself is a matter of usability.
Regards,
Sean