Greg Young has posted a link to a talk given about BDD by Scott Bellware which I highly recommend. I like it most because Scott clearly explains the differences between the two styles of BDD, one influenced by Dan North (*Behave) and one by Dave Astels (*Spec). I also like the fact that slowly but surely we're starting to use different terminology for the two types because mixing them up is (I believe) the cause of a lot of the misunderstandings regarding what BDD is all about.
My feeling, as I've posted before, is that both approaches have a lot of value but unfortunately the given/when/then style seems to me to be work best with some tool support (especially so you can parameterise the given/when/then itself) so it is harder to get into. I'm going to post more about my views on this later though.