A pretty good article on the controversy of modern human-Neanderthal interactions. The conventional orthodoxy that moderns and Neanderthals co-existed in Europe has been shaken by the fact that none of the Aurignacian archaeological assemblages, which were once believed to have been created by modern humans, are actually associated with modern human bones. So, the only way to associate them with modern humans is to claim that their sophistication makes it unlikely that they were created by Neanderthals, i.e., to presuppose that Neanderthals were dumber than modern humans and could not have created those artifacts. But, some of the Neanderthals' genes may persist in modern Europeans, so we shouldn't assume that Neanderthals were genetic dead-ends that had nothing (cultural or genetic) to offer to the first anatomically modern humans during their arrival in Europe.
On a somewhat related note, John Hawks writes about a recent conference on Rethinking the Human Revolution.