We talk, Apple listens. A little bit. The Mac Pro has been quietly upgraded. Nothing incredibly amazing, but quite a good jump in processor speed: Now you can order them with 3.33GHz Quad-Core Intel Xeon processors for a mere $1200.
You can also add four 2-terabyte hard drives from the factory, for $550 a pop ($350 to upgrade the default drive to 2TB). Unfortunately, this is not an architectural change, just a speed bump. [AppleStore—Thanks Michael Fisher]