I have an EtherRegen on order since early December. I'm going to try it. Here's why:
Recently I was building out a wall-mount rack on the opposite side of the front wall of my listening room. (I always told my daughter that her bedroom would become - my media room when she moved out.) This is conveniently adjacent to my network closet with my firewall and router.
In my planning, I'd decided to run a single network cable from a switch port in the network closet and then place a small switch in the rack that would supply the two devices (Oppo and streamer) with network access. This I did. And when everything was ready, I went back to the listening room to give my results a listen.
Digital streaming sounded awful. Brittle. Streaming local files was not as bad, but neither sounded like they had before my most recent modifications. Long story short, I removed the new switch and the system returned its prior performance levels.
The thing is, I've been working with networks for 30 years in my day job. I would NEVER have told you that I expected a switch to make a difference in the presentation of digital sound. But the answer, I think, is that switches can introduce noise onto the medium (wire), and some will more than others. Maybe your gear will filter out that noise, maybe it won't. My DAC is a Benchmark DAC3 HGC. It clearly doesn't capture it all. My streamer is a Tinkerboard S-based Volumio streamer that I built that normally sounds pretty fantastic. (Not expecting more than the standard level of galvanic isolation from that unit).
Converting to fiber and back comes with its own limitations on bit rate, etc, and in the end, it's two more conversions from the original format, so I'm a little shy about that approach.
So I ordered the EtherRegen. I don't know if I expect it to improve on the link that I'm currently using, but I still want a switch in my rack, and the Netgear device I'd purchased (been using them for years) wasn't going to cut it.