Some of the sites I read tend to update their news headlines. RSS-Bandit tries to filter out (group) duplicates, but rephrasing a headline or changing 4 numbers seems to be too much.
Therefore I'd recommend to search not only for duplicate headlines but also for dulicate links. The link to an article is imo more likely to stay the same on most blogs than the wording used for the title.
For web searches it's the same: I defined a smart feed that searches google news for some words (cool feature btw :). Everytime the search is executed it finds the same entries and happily presents them in a pop-up as new. Here i'd appreciate it, if you could come up with some enhancements as well to make sure only new entries will distract me from work :)