BBB slow and choppy on VNC

Hi, I have x11vnc installed on my new BBB shipped with Debian Wheezy. I tried to connect it through LAN and load a page with Chroumium. The speed is low and the user experience is choppy. It seems that the graphics is rendered on CPU instead of GPU. Or something goes wrong.

Could anyone please advise or share their GUI experience on BBB VNC please? Thanks!