I think the judges vote + public vote combo is a good one, the problem is that the judges have two bites of the cherry. As far as I'm concerned they've had their say in the initial vote, then the public get to vote and that should be it (IIRC it used to be like this - and yes you did sometimes get shock exits.)
The element of popularity contest would still be tempered by the leaderboard placings, but it would get rid of all this 'is it a fix' judges making mistakes stuff which is really very tiresome and detracts from the enjoyment IMO. (I admit to being as much of a 'fix' merchant as anyone - but I wish the opportunity for doubt wasn't there)
It's quite insulting really, the public do have favourites obviously but I also think they are perfectly capable of spotting a good dancer. And generally although some of the comedy turns probably stay in a bit longer than they should, by about half way through it is good dancers left and setting aside the Christopher Parker debacle. on the whole it is always good dancers in the final.
And since it is all good dancers left at the end I don't see why the public shouldn't be able to pick their 'favourite' good dancer to be in the semis and finals, instead of who the judges think we should have. If they hate someone and think they are crap - give them a score of 2 and state your reasons, then shut up.
Personally my favourite is Jay, I would be sad to see him miss out on the final because I think he deserves a place but I can equally see that any of Anita, Helen, Kellie, Georgia would be worthy finalists and put on a very good show if they are the ones to get through, and I enjoy watching them because I love watching dancing- and surely that's the same for most people who watch - we want to see the best dancers too - we can be trusted !