Everybody would always tell me to stay away from twist throttles on quads like the plague, and although I held off for some time, I finally gave in due to excessive thumb fatigue on my 06 YFZ450. Boy, was I glad I did! I have been using it for about 3 months now, and have had only one experience where an overshot jump caused me to unintentionally give it throttle. But the pros outweigh the cons. I no longer get thumb/hand fatigue, and I actually have much more control over the throttle than I used to.
The only negative part of this was the installation. On the YFZ450, you have to override the TORS system, which is actually extremely simple (they include a little black plastic looped wire that plugs into the wire socket to mimic the throttle, effectively eliminating the TORS system), after the hour I spent trying to identify the terms used in the instructions. The instructions are not vague, however; they are very precise. But you have to know what the terms mean, otherwise it will take quite a while trying to figure it out.
Of course, it is all personal preference, and the only way to find out is to try it. If you have never operated a twist throttle before, it will inevitably take some getting used to, but it is worth it.