I have to agree with David particularly when it comes to practicing technical studies. Why spend the time learning a Czerny technical study when the same stuff appears in Beethoven, and Clementi Sonatas, but as real music. Also, you must be very careful of Hanon. If practiced incorrectly, you can actually hurt your hands. Besides, his philosophy and technique were built around pianos that were substantially different from the modern piano -- lighter action and less resonance -- and music from a particular time period (published just 3 years after Beethoven's birth in 1773).
Actually it was published a century later.
Though I agree about not wasting time on the Hanon exercises (especially) as either an amateur or an adult student, since the little time at hand is far better spent squarely on good piano literature, in Cooke's Great Pianists On Piano Playing
Rachmaninoff says that The Virtuoso Pianist
was extensively used in the Russian piano school: http://books.google.it/books?id=tTcwi4d ... on&f=false