I dream about it too :)). I remember we talk about this in Gent. But what experiments are you talk about? How I can try it?
I think BDD programming can be much better and simpler with smalltalk because we are not limited with text files and code syntax. We can work with objects and present it with any way we want.
With classic TDD we model system specs with test methods which are very restricted way for building readable and reusable specs of system. And I think we mix here few concepts: how to validate (run) specs, how to persist specs and what specs actualy is. And last item is what we should reimplement from scrach independently from others (we should forgot about others for the moment). BDD exactly about it. But nonsmalltalk world continue mix concepts because text files and code syntax is only way to persist and build system specs there. They was make just good refactoring of TDD approach which is very nice but I'm sure we can do better :)