I'm a bit indecisive about that, it could simplify things, but if the object of reviews is to help authors improve and actually critic movies, they shouldn't it really be specific? I know we can still say as we like about whatever category in the actual review, but it would seem a bit of a hassle when we could simply state our mind through "1-10" kind of scores. I'm not sure if it's bad or good, but it might change reviews into a lot shorter ones, because people will simply review their overall views, rather go into details that might very well be helpful.
I'd do a test period, see how that works out, then make up my mind, good luck with that Tom.