edit: oh wait, yeah - the "For You" tab that has all those little circles to "tell us what you like". ITunes has almost 10 years of listening data, can't they figure that out for me?
With the multiple tab experience, you could browse into something on one tab, switch to another tab, and switch back, to see what you had previously browsed to (this is inherently how UITabBarController works). You can't anymore, you have to go back to the root to switch to browsing artists from albums, etc.
Another thing at all of the services completely fail at is disabling online music (iTunes Match, things not "available offline" on Spotify) when you have no cell service (i.e. on the train, when you're likely to be listening to music on your cell phone!). It's impossible to listen to streaming music at that time, so why even show it?
I'm old, I grew up with tapes and vinyl, I don't want to shuffle, I don't want to share my listening to facebook (I'll message my buddy when I've found a gem), I don't want to know what my friends are listenting to (my backlog is big enough already), I don't want crappy playlists (I have radio already, thank you), I'm too lazy to create my own playlists, and the last thing I want to do when running is listen to music.
All I would like to do is save a couple dozen artists I like so I can slowly dig through their oevre and it would be great to have a way to manage that (one endlessly scrolling list is not enough). I still haven't figured out how the play queue gets populated.
Finishing off with something positive, the wifi sync is pretty awesome, first time I got some music stored on my iphone (I use a linux laptop).
In iOS Music you used to need to go into the Settings app.
This should Just Work.
I'd love to be able to use one service that "solves" music for me but Apple Music isn't even close and I'm astounded at how botched the release has been.
So yeah. Your mileage may vary... quite wildly, apparently!