It works virtually 100% of the time. In terms of doing what it says, it gets 5 out of 5 stars. It WOULD be nice if we could customize the word(s) used to replace his name, and it would be even nicer if we could replace any picture(s) with our own selected content (there is a Chrome extension which allows for that, but I haven't found one in Firefox, yet). However, the app does not say that it does this, so that's just a wish list. It does what it says it does!