I'm very new here and only got about 4 weeks in GV's before this change but here is my take on it.
Using the keyboard is not unheard of in tanking games. Anyone who is familiar with Steel Beasts would be comfortable with using ASDW keys and the mouse for aiming the gun. I certainly find it much more finely controlled to use the mouse from the gunners position vs the joystick. I found using the joystick for driving before gave me more of a feeling of driving a tank but at the same time it seemed strange that I had to jump from the commander's position to the drivers just to stop or start the tank. A commander certainly can order "driver stop" and expect the tank to stop fairly quickly if the driver is awake.
The only thing that I've found a bit out of sorts was the fact that from the commanders position you can aim and fire the main gun very accurately on the move. I was able to "run and gun" a few tanks in the MA last night at close range which I think falls out of the realm of being "realistic" for WW2 era tanking. I was also able to shoot down two aircraft from the commanders position of the M4 using the Main Gun as well, while on the run. Hmmmmmm.
For me I like the keyboard driving from any position however I say let those that want the old JS control for the driver have the option. Also maybe reevaluate the ability of the commander to fire the main gun from his position.
JC