I tried a free trial of Deezer, which is a music streaming service similar to Spotify. I expected to start paying for it after the trial ended, but it turns out that I haven't. My reasons are:
1. £10 a month is too expensive. In fact, at £9.99, €9.99 or $9.99 Deezer is more expensive in the UK than any other region (and doesn't offer anything extra to UK users to make up for that). I'd be much more tempted for £5 a month.
2. Being a paying user makes you eligible to freely use something called 'The Flow'. The flow is a good idea in that it's a random dynamic playlist which should play stuff you like. This is exactly the sort of thing I want from a music streaming service. This is exactly the sort of thing a music streaming service can do far better than an offline music collection. I want to hear new music I'm not familiar with that's reasonably similar to the stuff I like so that I get a good hit rate.
But in reality it fails miserably to play things I want to hear, so I don't use it. I like metal and rock, but sometimes I also want to listen to Johnny Cash. Deezer's algorithm thinks this means I spend most of my time in the flow skipping past whingy American nu-metal and really bad country music.
3. I'd quite like proper support on my phone. Occasionally. I mean, like everyone else I have a fairly low data cap because mobile data is absurdly expensive, and a pretty underwhelming connection so I couldn't use it to stream music over 4g (if I'm lucky), but it would work over wifi. But "I have wifi but not a PC" is very much a special case for me, so it's not worth £9.99/month.
So overall: too expensive for what it offers.