Many think that the spec itself is crappy, so there's not much an implementation can do to fix that. Witness, for instance, the number of hardware vendors like Logitech that eschew Bluetooth in favor of their own proprietary wireless protocols.

I have no doubt the spec is crap, but some implementations are better (read: somewhat less problematic) than others. Which leads me to believe there is some degree of freedom with respect to quality here.

I fully agree with you there. I'm working on some BT stuff, and find it to be lacking, mainly the software stack. The spec looks ok for a wireless interface, the quality of the stacks are all over the place.