I've seen this mouthpiece on several sites, since I tend to gravitate towards Japanese things, I was naturally very curious about it, so I bought it for my soprano saxophone. I can say that it not only compliments the natural unlacquered patina of the saxophone, but it also sounds really great. I'm not especially fussy when it comes to sound. But I do like a warm, expressive sound for jazz, and the Aizen SO Mouthpiece definitely has that for me. I've tried mouthpieces that have a "muddy" sound, almost as if the reed is barely vibrating against the mouthpiece. I've also tried mouthpieces that I couldn't even play, even after trying all differing strengths of reeds! So for me, the Aizen is ideal.
My only complaint with the Aizen SO soprano mouthpiece, and I assume all Aizen mouthpieces are alike, is that it does not come with a cap and ligature. It was tricky to find one that fit well and held the reed firmly in place. I ended up going with one of the Francois Louis ligatures, but it's tricky to put on sometimes. For what Aizen mouthpieces cost, they really ought to come with a custom made cap and ligature.