Hi Guys
I'm not going to speak to the reliability of fuses because quite frankly I've never had one blown or cause damage to any products. Maybe that's me just being careful. However I have had experience in how they sound as well as how they change sound depending on a few mechanical adjustments and material choices. I've now done fuse swapping on over 10 amplifiers and at the end of the day (2016) yes they do sound different and yes they do sound different per amplifier. Directional? Yes they actually are directional. But, can be trained to go the other way, just like cables can (some cables).
If I were to give a caution it would be these, watch out for the upward shift in tone and keep your ear on the bottom octave as the wrong fuse will get phazy sounding. Also keep an eye on your stage, because when you make a fuse change you are also going to make a speaker placement change more then likely, or even cable change. "everything affects everything else".
Michael