Yes, now the studies of some consulting firms (MusicWatch) are coming out directly focused on users who listen to Apple Music and the best of all is that are totally unrelated to Apple. It is clear that Apple does not release a pledge of reception figures for its products or use of its own software until they do not want to and for now they still do not refer to the sales of the Apple Watch and the users who may be using Apple Music that is still within the three months free.
After Apple launched its streaming music software Apple Music together with the Apple Watch, many were those who commented that this Apple music service would eventually take users of existing music streaming services such as Spotify, Rdio, Pandora or similar, but users who didn't pay to listen to music might not switch to Apple's service. MusicWatch ensures in its studio that only one in 10 users uses Apple Music, they also ensure that 64% of users who use it will continue once the trial period ends and that 61% disabled renewal after three months free.
We are clear that these types of studies are indicative since they have been carried out in the United States and on some 5.000 users over 13 years of age. Obviously you can get some varemos that can be close to the real figures, but Apple Music is still free and personally I think that so far this does not become a paid service, all these studies are rather not very useful to see the differences among these music services. By the way, Apple explained through its spokesperson according to The Verge, that 79% of users who signed up for the service continue to use it today ...