Adobe has released a plugin for Photoshop CS4 that disables Macbook trackpad gestures because people have apparently complained about triggering gestures accidentally. From Imaging Resource:
On MacBook Air and recent MacBook Pro systems, Adobe Photoshop CS4 reads multitouch gestures to rotate of the document canvas. But it's easy to accidentally rotate the canvas on newer trackpads.
To address the problem, Adobe has released a plug-in that disables the multitouch gesture for canvas rotation and the gestures for zooming and flick panning. Canvas rotation remains available through the Rotate View tool and Photoshop is otherwise unaffected by the plug-in, the company said.
Link: Adobe Releases Plug-in to Disable Multitouch Gestures.
This is one of the trickier parts of developing and testing multitouch gestures. You not only need to make them work when a user wants them to, but you need them not to work when a user doesn't want them to.
People using a laptop equipped with a multitouch touchpad will still spend almost all of their time (probably 99% or higher) doing the normal things — typing and pointing. But their other fingers and their palms are always moving around very close to the touchpad, or even resting on it. A single accidental flick, pinch, or other gesture can be very disrupting and can even cause big mistakes in the user's work.
A usability tester's job in this case is to measure the rate at which accidental gestures occur. That's tricky when even a very low rate, like one every few hours or one a day, could be higher than is acceptable, so you can't measure that with a short usability test in a lab.
Update: Another new MacBook user complains about accidental pinch gestures: room34.