Love the Spotify iOS apps. Smooth as butter on my iPad Mini. I can tether my WiFi only iPad via Bluetooth to my iPhone to maintain cellular connection integrity (for validating the local files stored on it). I can also run Spotify directly on my iPhone, but the solution outlined above gives me access to the bigger real estate offed by the iPad Mini App.
You’ll need to go Spotify Pro to utilize the mobile capabilities, but if you’re not locked into the free version of it on your desktop already, you don’t know what you’re missing.
I have an older model Video iPod with a sixty gig hard drive. The unit still works, but the display has gone belly up. There are thirty odd gigabyte of songs locked away on that device. I noticed an option to sync my iPod to my Spotify a couple weeks ago, so I dug out my iPod and ran it through the Spotify sync. Voila, I’ve now got all the music that was locked in that iPod added to a local files list on Spotify! The only catch was that my previously purchased iTunes were “locked”. The solution was involved loading up iTunes.
I hadn’t fired iTunes up for so long I was unaware that they now let you re-download all your previous music purchases. In a few minutes that process was completed, and now I’m back in possession of all my orphaned music.