Personally, I think men will "catch on" in the future. Many of the Pinterest users I know use it as a catalog of things they like around the web. Sometimes it's clothing/craft/recipe related, and sometimes it's a workout program, news story, or other interesting (and gender neutral) read, that they want to come back to.
The fairer half are a grossly underserved audience, there are lots of opportunities and I hope Pinterest is the first of many to build on it.
EDIT: although second thought. Pinterest strong side is that women (more than men) like to collect stuff. Nice thing about Pinterest is that you can pinboard your collections, join others, etc. I am not sure if the same effect would work on "mens pinterest".
I don't think a men-only version would work anyways. Men just don't tend to 'window shop' like women do. Men also don't like sharing as much as women do.