I find no difference in sound quality between Qobuz Connect and my other streaming apps -- the music is still being delivered digitally from their server to my player. QC is just a controller for selection. But I'm probably as picky as some others.
It's a fine app, but the one drawback I have with it is that it has no access to my local collection or the radio stations we listen to (classical & news). Particularly with the local collection, some of my favorite material is not available on Qobuz (copyright, never released, transferred from LP/open reel, personal recordings) and I like to build personal playlists that include both Qobuz and local material. So, I still need the other apps. However, QC is a nice app and glad its finally out in the wild and working.