Oh wait, I see there's a hardware screen orientation lock switch now. (safaribooksonline.com)
Update: You can now enable the iPad orientation lock switch in iOS 4.3, this is allows you to adjust the side button to be either a rotation lock or mute button. (osxdaily.com)
Just like the Apple iPad, the A1 employs a physical volume rocker and screen orientation lock switch on its left edge. (cnet.com)