Many people agree on the words proposed by GoF, but not on the details of the meaning, and this is a frequent source of misunderstandings and useless debates. Over the years I have gone from fan of the book to considering it a net negative force in software engineering, a failed attempt that many people still believe in. (The other failure of the book is in educating people to blindly believe that applying a given pattern is always a good solution because, hey, it's a pattern)
If you look at the details of the patterns as examples rather than definitions, and treat on the book as a general description of common situations, problems and approaches, then all is well.
If you look at the details of the patterns as examples rather than definitions, and treat on the book as a general description of common situations, problems and approaches, then all is well.