With respect to whether and how the spores were weaponized, I have both feet in the weaponization camp, having reviewed numerous anthrax epidemics and seen nothing like the Senate letters' effect elsewhere, except Sverdlovsk. Yeltsin later admitted the 1979 Sverdlovsk epidemic resulted from a leak of anthrax from a biowarfare program.
However, the problem remains that nearly all research on weaponization is unavailable in the open literature. Although we can make educated guesses about how the letter spores may have been prepared, the only way to be certain is to experimentally demonstrate that a particular method produces an identical product. While the FBI waffles about how Ivins could have dried the spores this way or that way, and they don't really care how, FBI has failed to demonstrate that any of the methods they don't care about would yield the correct product. FBI has further failed to demonstrate that Ivins could dry and prepare the volume of spores used, within the window of time available between September 11 and the mailings.
The new field of forensics has led us to a flask available to hundreds. The old field of weaponization could narrow down that number of suspects considerably, but has remained unexplored.
Since the weaponization field of study is classified TOP SECRET, it will require a classified venue to review this material. What is needed is a scientific and investigative review of the evidence, keeping in mind that this "black art" may be encumbered with more than its share of dis/misinformation.