I have just purchased one of the three T5.7's in the US. I have not sailed it yet but I have done a lot of research on the boat.
From everything I have read the Taipan has the ability to keep pace with the Tornado and most of the other 20 footers with sailing ability becoming the deciding factor. The biggest problem with the 5.7 is keeping it depowered enough to be effective when the wind starts to blow. The boat was designed specifically for a heavy crew (over 150kg/330 lbs). The new F18 Capricorn did trounce the 5.7's in the Aus Taipan Nationals, showing that hull design is more important than being lightweight in this case, the Capricorn being 80 pounds heavier to meet class specs. Everyone that I have talked to that has sailed one has really liked them and the speed that they produce. I am very excited and proud to own one and can't wait to put many miles on it.
AHPC's Taipan 5.7 page
TAIPAN CATAMARAN ASSOCIATION OF AUSTRALIA