Hey, I'm working on that one too! That one not only forces you to have your scales and arpeggios together, but string skipping too. Quite a workout as well as a magnificent piece of music. Another Bach piece I'm working on is Prelude #3 from the Well Tempered Clavier. The 4th, 5th and 6th intervals, if played on adjacent strings, are rather demanding if you use a flatpick. The ending run is tough as well. I can't quite get that piece up to speed yet... YET!!!