Comment 18 for bug 228054

Yes. The Fn keys bring up OSD, but functions differ somewhat. Volume and brightness are controlled by repeating keystrokes, while in the original design they were controlled by the scroll wheel. Four Fn keys are used instead of original three; instant mute and going back to original volume after unmute is not available.
Original (Sony) key binding:
Fn+F3: mute/unmute
Fn+F4: scroll wheel controls volume
Fn:F5: scroll wheel controls brightness
Fn:F6: no function

Current binding (10.04 Beta1):
Fn+F3: decrease volume, muting after reaching minimum
Fn+F4: increase volume by repeating Fn+F4
Fn+F5: decrease brightness
Fn+F6: increase brightness