I have a wonderful laugh with this tool, posting various bits of my WIP into the thing. Sometimes, the so-called "cliches" can be a bit ridiculous given specific contexts/other such "situational" elements, but then again...
If you include a < in your text, it barfs up a "Server Error in '/' Application." Is there a way to contact Mr. Mitchell and tell him about this?
So far, my current short story has two cliches: "go crazy" and "to be honest." I don't think either of them need to be removed. (Really, if you need this tool, you've probably got bigger problems than tired phrasing.)
The usefulness will vary widely by individual, I suppose. They're really only good insofar as they point out things you didn't already know. I tend to choose words fairly carefully, so this tool isn't likely to pick up something I didn't already realize was there and haven't already made a decision about.