It depends which film you choose as to how noticeable it is.  The film we have on the front gable glazing is deliberately noticeable, as we wanted to add some privacy as well, so opted for a stainless steel like finish, that turns that glazing into a dull mirror from outside.  The bedroom window glazing film is a barely detectable film, that most people wouldn't notice unless it was pointed out to them.   @PeterStarck has had the same almost clear film fitted to some of his glazing, I