I don't own this, but I used it for the first time yesterday with my 60 pound, 1.5 year old Chesapeake Lab Mix.  It has to be the greatest toy ever.  Not only do I not have to pick up slobbery tennis balls anymore, but I'm not throwing my arm out either trying to throw it far enough for her to actually get some exercise.  I'm considering purchasing one just so I can save my arm in the future and also because I can't throw that far.