For those who like this sort of thing i'd be frightened to be the person sailing in front - look out for those plastic bags!! http://www.boardseekermag.com/equipment_reviews/equipment/starboard_tandem_07.htm
It was a blast to sail and planed up in around 8 - 11 knots (rider on the back 9.5- rider on the front 8.5)
Managed to gybe it first time but you can come unstuck with longer booms. A great feeling when you get the team work going. It planes and its fast!
Scotty Mckercher and a co pilot were sailing it at Sprecks in Hawaii with 5.0 and 4.5 and getting some medium jumps on it - although jumps arent really functional.
It would be super easy for a beginner to stand on the front and let the sailor on the back do the work. These will be great for windsurfing schools. The shop formerly known as Pelican Point has ordered one so it will be avaialable down at PP during the summer.
Team racing a fleet of these would be a total blast!