UQD, I think there might be something to the "new atheism" concept, and I think you touched on it as did morningpaper - Russell and his peers took a more philosophical approach, he gently tried to apply logic to particular instances of theological ideas, he was deeply respectful of religious beliefs even if he didn't agree and so on. You could say that he took on religion on religion's turf. He took religion to task for what religion professes to uphold and professes to believe.
Dawkins, Hitchens and the rest take a very different approach which may be best summed up as "You believe what??? FFS..." As you suggested yourself, these people see a Russell-type discourse as spurious at its core. I think Russell saw atheism as a (more or less) equivalent belief system to religion; the "new atheists", if I may use that term, see atheism as profoundly distinct from religion.
More importantly, they also take on religion for the observable effects religion has on people. Russell would (say) do a philosophical discourse on whether heaven and hell are useful goals for a person. Dawkins (and Hitchens, in particular) are much more likely to say that not only are heaven and hell complete but, hey, look at what troubles are caused by believing in them, too.
Atheism itself hasn't changed, as it's a desperately simple standpoint. But I do think there has been a significant change in how openly and readily some atheists will now dismiss religious beliefs entirely.
For what it's worth, I like it. I don't agree with everything that Dawkins says, and I certainly don't agree with a lot of what Hitchens says, but I'm glad they're out there and I'm very pleased that they're getting platforms to say what they think.
When I was 14 and mentioned in a school lesson that I was an atheist, my teacher furiously shouted "You're too young to decide that!" Yet, strangely, other people in my class weren't too young to claim to be Christians or Sikhs... Having the likes of Dawkins on TV, and his books in libraries, is giving lots of people the tacit permission they need to throw off their religious beliefs if they want to and to see the world in a different way.