Current Qobuz user and I just pre-ordered Apple Music for this.
I think a lot of the appeal of a dedicated Classical music service is discovery or context when listening/searching. For instance, if I want to listen to and investigate a Shostakovich piano trio, I'd like to be able to see all the versions available and some background on each. Also, some like to focus on a conductor or a particular symphony orchestra or a lead musician rather than the composer of a work. There are also catalog numbers. It's just a different environment.
I have the free Idagio account but never use it. Qobuz hasn't been terrible re: classical but the onus is on the end user to really know what they are searching for.
I am concerned that the streaming quality of the Apple Music plan won't be great or that I'll have trouble integrating it into my system.
JS