I purchased two Swiss boxes replacing Purple and Master SR fuses. They are now pretty broken in and I love them! I have a Graphene Sluggo on my Int amp and pure copper Sluggos on my field coil power supply. The copper Sluggos are definitely directional. I have not found the Graphene Sluggos to be directional in my amplifier.
The SR fuses are wonderful, but the Swiss box does not editorialize or color the sound in any way. All SR fuses have a sound and personality if you will. Using them I was forced to find the recipe or combo of fuse colors needed for my system and tastes. None of the recipe tailoring is needed with the Swiss box.
All aspects of sound quality have improved with no part of the frequency spectrum highlighted. As others have said, music has a greater sense of ease and is naturally and rightly balanced. The Swiss box improves dynamics, realism, resolution, stage size and just puts a smile on your face.