How do you use hook_query_alter to get inside a query's creation?
Just to close this item out: It appears that my definition of hook_query_alter was, in fact, working correctly.  My problem was in assuming that I would be able to do things like  dsm($the_query) and see the components of the query object in preparation for doing stuff with them.  This doesn't seem to be the case -- dsm() wasn't returning anything of real use other than alterTags, but the orderby() (and other similar actions) did in fact alter the query.  So, I'd argue that it's a bit confusing, but works-as-designed, I guess...