I have a different throttle on my bike (7/8" bars), and it is a Magura Duo throttle. It has a 1/4 turn side, and on the other side you can get a faster throttle. These throttle are mostly used on racing or Off Road motorcycles.
http://www.ebay.com/itm/Magura-Duo-314-Throttle-Grips-Motocross-AHRMA-VMX-Hus...I use the 1/4 side, and JOG is correct....it is harder to hold a steady cruise speed, as a small movement of the throttle makes a bigger change at the carb.....I suspect that is why most street bikes don't use 1/4 turn throttles.
It also requires more strength to turn....as the grip movement does more work as it moves, and this can get tiring on long rides.