In terms of liking people, I think most viewers have an idea of how Strictly should be done 'properly'.
So if you imagine a score out of 100, I give roughly 20 each to being good ballroom and Latin, then the remaining 60 is stuff like enthusiasm, relationship with partner, improvement, interest in the dancing (I think it was maybe Jodie Kidd who became one of my favourites after she went on ITT and had learned the names of all the different types of walks in the rumba).
And the closer to 100 you get, the better. So some people score really highly in the dancing, but not in the other categories (Louis Smith, Maisie). Others can make up points in the later categories (Susan Calman, Jamie). Then some are good in all of them (Alesha, Debbie McGee).
Everybody's proportions will vary, and of course you have to add predjudices on the top (Ranvir and Victoria Pendleton got initial boosts for being local, some Americans lose marks in the enthusiasm section for seeming over-gushing etc).