While on a Sartharion 25 raid this past weekend, I noticed one of the other Rogues in the group moving very peculiarly. It took me a second to put my finger on it, but I figured out what was happening. He would be running around normally, and would then stop in place for two seconds every time he used Fan of Knives. I sent him a friendly whisper, asking why he was pausing when using Fan of Knives. He replied back that he had to stop moving and click the FoK button on his action bars, of course. I asked why he didn't simply bind FoK to a key for easier access, and he replied with "My 1-9 keys are already full!"
Many Rogues spend hours choosing between different gems and weapon choices, when often the difference is less than 1% of their DPS. I see the control aspects of the class as more important than gear choices (not that gear is unimportant!). Without the ability to perform your rotations and combinations with finely-tuned timing, you could be losing as much as 25% DPS on certain fights. Making proper use of key binds and user interface addons are crucial to maximizing your DPS and reaction times in PvP.