They all have their quirks, but until airsonic-advanced catches up with the latest opensubsonic API, I’ve been trying out Audinaut and DSub.
Subsonic doesn’t work for me, I’m guessing because it refuses to fall back to earlier versions of their API. I could be wrong.
About the PIN thing – I was confused too, because they never bother explaining to anyone. What actually happens is their system automatically e-mails you a new verification code (not a pin, if you ask me) while you’re on the phone, and you need to remember to check whichever e-mail account that is and continuously refresh until it comes up.
It doesn’t help that e-mail, like SMS text messaging, while being very fast is absolutely NOT an instant communication method. There can often be delays receiving a message with those technologies due to how they’re designed.