What recommendation systems stand out as the most effective/relevant to you guys? These can be largely explicit feedback based systems (ie Netflix), implicit feedback based (ie Amazon), social graph based, etc.
Not looking for RMSE metrics or traffic driving numbers as much as subjective personal opinions.
It's not because of the content they show me, but rather because of the accuracy of their "predicted star rating" metric. Netflix showing me a broad spectrum of content I can immediately parse through by looking at predicted ratings combined with all the other standard quality metrics I look for has led me to find an immense wealth of content I never would have guessed I'd like.