I had a listen to this at the back end of last year and thought it sounded amazing. It really brought out a lot of detail in my speakers (b&w 702 S2). In the end I felt the price was just a bit too high to justify the purchase.
I ended up going for a second hand Naim NDX which has replaced the multichannel setup. Cometely agree with you on that one, I love the sound and haven't looked back since I swapped.
When it comes to the app: I think it's excellent, very user friendly. As you highlighted the Spotify integration is not as good as the Tidal integration. I'd really recommend getting a Tidal subscription (or at least a free trial) to use with the Naim app.