I've now been using a Uniti Core for a few months. An excellent bit of kit; I much prefer it to a Innuos Zen Mini. The Uniti Core is often labelled as expensive. it is indeed costly, but if you price up an Innuos that can have a SSD (which is removable in the case of the Naim)and has a linear power supply (plus it built way better), the price looks more reasonable. OK, it's a network player, not an internet streamer but I didn't really rate the Zen Mini as a streamer, to be honest. The Core is absolutely silent, unlike the Zen Mini. An important consideration if the server is in the same room as your hifi.
In use, it's been extremely reliable. Most CDs I've ripped on it have done so without any problems. 2 out of around 500 or so reported a single error, but this was eliminated with a 2nd rip. It uses I think 3 online databases for metadata, which usually correctly identifies album, artist, etc.. It's easy to edit meta data with the Naim app and change album cover. Note though that you can't use the Naim app to edit meta data which was acquired by means other than the Uniti Core.
If you're using a Naim streamer it integrates with those seamlessly, including an excellent Tidal integration. For example; when selecting the Core the app will show others albums by that artist from within your collection, or on Tidal. It will also suggest other similar albums on Tidal.
I have tested it as a UPNP server against exactly the same FLAC file stored on my MBP (on the same network) and served by Asset UPNP. It's quite easy to tell the difference, with the Naim being 'better' in my opinion. The other playback method is from the Core is via coaxial SPDIF. I did test that in to my NDX2, vs UPNP. No difference that I could ascertain.