Although this article has some errors (can you find any?), there are some very interesting parts to it. It correctly discusses the Neanderthal male-modern human female infertility, and mentions that Neanderthals were never very numerous, with estimates of peak population as low as 3500 females.
As for the errors – the part I disagree with the most is the assertion that chimps are genetically more similar to us than Neanderthals (the article claims chimps are 99.8% identical to us while Neanderthals are 99.7%). Chimps, in fact, are less than 98% similar to us.