I did the upgrade from PW to DirectStream shortly after the upgrade kit was available. While I groused about spending the money...it was absolutely worth it...much more "analog" sounding, even crappy mp3s sound decent because of the up sampling to DSD, CDs sound better than ever...more detail, more instrument separation, better bass., soundstaging is improved. I have not used high-res digital files with it.
I've got a revealing system with Wilson Sophia 3 speakers and it doesn't hide anything.
Going from PW to DirectStream was worth the money..it is not a subtle change. On a scale of 0 - 10 where 10 is a new piece of great equipment, the improvement was a solid 5 IMO.