[ileitch]

Also, if you avoid the normalisation step you could easily factor in the degree at which user A liked the quality vs. user B, instead of just a 'more' or 'less' question.

If you factor your vector weights by the scale of your quality rating (0 - 10?) then if user A liked the quality film X vs. film Y +6 more points than user B's +1, this would give you a more accurate correlation.

Anyway, food for thought. A very fun problem to be working on!