Not really. It's noticeable over Bluetooth as well, if your device supports codecs with a high enough bitrate. Obviously Bluetooth is still lossy, but listening experience is way better. The headphones I'm wearing now use aptxHD, with a bitrate of 576kbps. Spotify only offers AAC, with a bitrate of 256kbps.
As far as who can appreciate the difference, I guess? But you don't need to be a concert pianist to appreciate audio. That said, I play many instruments, so maybe I'm biased.
I'm not going to argue conjecture. I have over $10,000 in audio equipment and like I already said I play many instruments, so you're not even picking someone good to make generalizations about. Bluetooth codecs are always going to be subpar, but they're probably how most people listen to streaming services most of the time. Anything that is streaming from a PC except Bluetooth is a notable difference.
I just checked the headphones I'm wearing again, they're actually using aptx lossless with a bitrate of 1200kbps. The point is that Deezer offers the same services for less money and higher quality audio streaming.
Apparently, when Spotify does roll out hifi, it will probably be a higher paid tier. Until then, for me, Deezer is the far superior service.