Microsoft has been sending conflicting and ambiguous messages regarding these products for some time.
At one point they attempted to make the distinction between designers and developers, but let's face it, I have yet to see a small to mid-sized organization that had that separation. In reality we often wear both hats. So to me it just makes sense to be able to have the right toolset available to accomplish the task at hand.
You can catch all the details at Somasegar's WebLog.