I would strongly suggest staying away from it.  We'll use it for ORM purposes sometimes when the KW diff is really low but for the most part stay away from it as it will most likely get you dinged for duplicate content... no bueno

HOWEVER.  If you still need to scrape other RSS feeds... make sure to give attribution and add a robots noindex meta tag to each page where content is republished.  That way you can hopefully sidestep any and all negative penalties.