I'll keep this short since, well, it's a cable.
I got it as part of the X5 stacking kit, to pair it with an E12A, replacing the original cable that came in with the unit (the L8). I imagined it's just going to be a pretty cable, but I was pleasantly surprised to actually hear a difference.
In a nutshell, compared to the "generic" audio cable, what I subjectively heard:
1. The highs became more audiable and clearer, but not fatiguing. I'm very sensitive to the latter so I guess that's an accomplishment.
2. The overall sound became slightly more detailed.
On the bad side, while the actual gold and silver connectors are gorgeous, the cable itself has a semi-transparent sleeve, which kind of looks smudged. Additionally, similar to Fiio's headphone cables, the silver plug can be screwed in and out for some reason. That's not really a drawback (I really don't know its functional purpose), but I thought I'll mention it here anyway.
To sum this up, I'm actually aware cables do make an impact. The improvement in audio quality with the L16 isn't day and night, but it's there and it's not hard to notice. I know that some companies out there are selling similar cables, sometimes for hundreds of dollars, and they aren't ashamed to claim you'll hear a difference worth that sum.
For the L16's price though, I believe you get your money's worth: A subtle improvement in sound quality without a hole in your pocket.
Test setup: Laptop USB > Fiio X5 > [L16] > Fiio E12A > Shure SE535.