you are talking about transposers there are 2 different kind of transposers if I am correct there is the one that uses the button and it transposes and then there is that one who can transpose by knowing their key signatures and move to whatever key they need to move to correct me if i'm wrong I can't play and that's all my fault but that's another story 
forgive my run on sentences 
On this board, when we mention "transposers", we're mainly talking about the people who use the transpose button because they can only play in one key. This is the kind of person of which this thread is addressing.
As you can see, there are 15 pages of varying viewpoints on the subject.
