My observations are kind of all over the place so far. It has been a busy day without much sit down critical listening. Demanding detailed pieces are where, to me, the Sierras shine. Remember when you got your Ascends and went through all your music again rediscovering it and all the things you never heard before on familiar discs? That is what it is like for detailed demanding pieces. Then for simple stuff the imaging, sound stage, and bass are what you notice most. But, then I played some of the Jewel concert, just her and her guitar for the most part, I have in HD on the DVR and it was like holy crap that was amazing compared to listening to it just 2 or 3 nights ago on the 340s.
The Fairfield Four's Standing in the Safety Zone was the disc that impressed me the most today for what the Sierra can do. The four part harmonies had more separation of the individual voices and the depth of the timbre, that I had not been hearing before, was captivating on the Sierras.
Oh and the Sierras can play LOUD with no strain. I started to worry if I was going to run into clipping.