Multiple sorting parameters in query_posts?

Is it possible to pass multiple orderby values in the query_posts? I want to display the first 3 entries of my products custom post-type, and prioritize to list the ones with higher ratings (a custom field value), but also be random, so it’s not showing the same 3 posts every time. Is there a way to do this?

On the other hand, would it be easier to create a custom taxonomy for the rating, and only query posts from the higher rating categories? But how would I have it check lower ratings if there weren’t enough in the highest category?