If the prototypes of the new iPhone we've seen are generally accurate, I really think the move from the rocker volume switch to two dedicated volume buttons opens up a lot of possibilities. I can see being able to navigate through lock screen information like missed calls, e-mail, or texts (if that's added eventually with OS 4 or later), or have each button serve as a quick launch replacement for favorites or add further customization such as being able to call a single contact or launch a particular application.
I have never had any issues with the current volume rocker and I think it works great. The only reason to make the change to dedicated up/down buttons would appear to be to add functionality to them by allowing them to easily be used as two distinct standalone buttons.
I think Apple realized they couldn't add any additional buttons to the iPhone, so the only way to increase options/functionality was to take existing buttons--the up/down volume rocker--and increase their usefulness and functionality.
I have never had any issues with the current volume rocker and I think it works great. The only reason to make the change to dedicated up/down buttons would appear to be to add functionality to them by allowing them to easily be used as two distinct standalone buttons.
I think Apple realized they couldn't add any additional buttons to the iPhone, so the only way to increase options/functionality was to take existing buttons--the up/down volume rocker--and increase their usefulness and functionality.