Ebert's review seems rather cynical. Ten years ago he liked what Scream was offering up, he rated the first three films highly. I don't see anything in his review that necessarily contradicts what he said about the others. Perhaps he's just rating it low because it's the fourth installment in the series. He never really rates any fourth installment that highly anyways.
Surely, it can't be any worse than the 3rd one. The first two really good, but, IMHO, the 3rd one lost it's way
Most of the reviews I've read say it was better than the third one.
At the very least, this is Kevin Williamson's story, with the third one Williamson had little to no involvement with the film. I don't expect it to be better than the first two, but I think it should be at least better than the third.