Most everyone I know has some kind of personal music collection on their local machine(s), and the streaming is a complement to that. Because of the general hassle associated with managing a large and growing music collection, of course we'd love to offload that to someone else for a nominal fee.
My current strategy involves tripling up on cloud storage and trying before I buy any of the streaming services. Google and Amazon both offer substantial music storage for ridiculously low prices. $20 a year for a cloud drive with UNLIMITED storage means a one time hassle of tagging and uploading everything to the cloud...let them worry about it after that. Amazon is the winner now, just because of the download capability. Google Music is great too, though. Both work well on your mobile device with limited bandwidth requirements.
After investigating and playing with Spotify a little bit, it actually appears to be an inferior product to MOG [assuming you plan to pay for either service] for a few reasons, which you can seek out for yourself and come to your own conclusion.
BitTorrent and File Lockers aren't going away. Turntable.fm is fantastic. We've got options. Let Spotify do whatever it wants, and we'll do whatever best suits our needs/wants.