We have released this module with several sites in Acquia recently and it had us scratching our heads, because there were seemingly random cases where it simply didn't work.

Acquia (and others) reccomend setting the $base_url variable in settings.php for security reasons, but you should NOT do this when using this module. If you do, the page will be cached using the $base_url as part of the cache key, even on alternative domains that would otherwise be redirected. That means that the domain_301_redirect_init() hook will not be ran while that page is cached for anonymous users and the alternative domains will not be redirected. The results will be sporatic at best.

I think it would be helpful if there was a little warning somewhere about setting $base_url manually in documentation.
Or alternatively, a check to see if the global was set manually when you visit the admin/config page with a warning message about doing so.