They're just studies and they won't replace working on real pieces, but
much more interesting and musical than anything I found in Czerny.
But... why to play studies if you can play the same dificulties with real pieces of music? For example: the 3º mouvement of the moonlight of Beethoven is dificult? But you may play it, training it. Why loose your time with studies of harps to play it? You may play the harps of the sonata and doing so you learn harps and you have a very beautiful sonata studied...THE ONLY STUDIES we must learn are Chopin Studies. Because they are real and beautiful Music.And you have Bach. If you can play Bach you are able to play everything...