It's my dilemma of running Manga Studio 4 EX and Sketchbook Pro 2010 on my Windows 8 RC installed devices: I have to choose one app or the other. The situation happened because Sketchbook Pro 2010 runs properly on the default tablet driver, but Manga Studio 4 EX requires me to install the WAcom driver. Once I installed the Wacom driver, Manga Studio 4 EX will work great, but Sketchbook Pro 2010 will fail to have any pressure sensitivity. So that means I have to choose, either use the native tablet driver, or the Wacom driver.
Damn you ... whoever caused the problem.