Yeah, I'm in the middle of getting most of my catalog on iTunes/Spotify/etc right now (annoyingly large amount of paperwork). I honestly have no idea on what to expect. I know there is a large portion of people that only listen to these sites for music. For instance my kids only use Apple Music and in their eyes it has everything. The concept of spending money on tangible music is mind blowing to them even though they've been around it forever at the house. But they will easily give their last $10 to Clash of Clans upgrades or something - which I think is a total waste.
I'm in the same boat as velcro (never thought I'd say that) in that I use Apple Music the most right now for work since my car got broken into and iPod Classic was stolen (had that thing for 7 years, fuck). I used to rip all my records to MP3s and load em up on that. Now all I have is my phone (with no storage) so I'm stuck with it for now. Every time I find something I didn't expect to see I just throw it in a playlist. There's obv TONS of useless shit on there but there's also a bunch I wasn't expecting to see - stuff new and old (Ex: Ivy Green, Violent Change, Flesh World, Golden Pelicans, Goner Catalog, Gino and Goons, Life Stinks, Manateees, Crime, Kraut, Feederz, Bored Teenager Comps, Soul Jazz punk comps, etc). If all that stuff wasn't on there - I'd be dying.
Bandcamp is great for new stuff but isn't as easy to navigate or just hit shuffle once in the day and let it go. I also read that SoundCloud is having troubles. I know a lot of people use YouTube for listening to music but that's still such a foreign concept to me. I still see YouTube as a place to watch people getting hit in the nuts.