PrimateLabs provides some early Geekbench 2 benchmarks on the just-released 8-Core "Harpertown" Mac Pro at 2.8GHz compared to the old 8-Core "Clovertown" 3.0GHz Mac Pro.
Despite the slower clock speed, the new "Hapertown" Mac Pro outperformed the older "Clovertown" Mac Pro in Integer, Memory and Stream performance, reflecting its faster memory (800MHz vs 667MHz) and bus (1600MHz vs 1333MHz). The new Mac Pro, however, did lag behind in floating point performance, compared to the older higher-clock speed model.
Apple introduced the new Mac Pro earlier this week.