I am a latecomer to the string but would like to add my two cents:  The rule only says that the pilot must inform the "tower" that the aircraft is experimental.  Nothing about any other ATC person.  I have from the beginning referred to my aircraft as a Lancair or Lancair Legacy for the obvious reason addressed in other posts: it conveys information that could be useful to the controller and others on frequency.  The term "experimental" is useful only it one assumes that it is important for others to "know" that it is put together with chewing gum and could fall apart at any time.  I think I am within the letter of the law except when talking to tower operators.  I have asked a number of them and have never heard an expressed preference for "experimental."  Because they cannot advise me to flaunt the reg, I most often hear that they are fine with either.