See also the links in the article to the discussion on domain hacks at NamePros, and to an earlier article I did on domain hacks.
As general commentary, I would consider how business applicable and valuable the word is (the entire word including both sides), by examining things like number of corporate listings, registered TLDs, developed TLDs, etc.
But part of the beauty of a domain hack is how elegant it is - some words split better than others. Evaluating the aesthetics is not always easy. Note: I have no domain hacks personally, well one very poor one, but see beauty, creativity and applicability in them.