I've always found the iOS Music app superior to pretty much everything else (including Play). Obviously it doesn't have streaming but as a player the UI is much better. I find Play quite confusing and it wastes a lot of space (e.g. the artists screen - I don't need to see a photo of the artist with their name, it doesn't add any value).
You can use the app perfectly well without ever going near the desktop iTunes software, as you say by buying music through the device, or using iTunes Radio.
If you have other music you want to load, the yes, you need to use the desktop app for that.
What's your point?
iTunes is only required if you want to add your own music.
edit: I'm pretty sure iTunes actually uses a cached progressive download, but the difference is academic.
I’ll stay on Rdio.
I really wonder why Google does this. It took them months to release the iPad version of their Maps app, with very few UI differences. There's something broken about that workflow.
Not quite as bad as the oft-promised Google Drive for Linux, but still.
This applies a lot more to Maps than it does to Music, of course.