From:  dpreview.com

"Supersonic Wave Filter"

The "Supersonic Wave Filter" is a method of cleaning the sensor which
involves making it vibrate at a very high frequency, this vibration
causes any dust or dirt to literally drop off the sensor surface and
on to a sticky tape material (which apparently has been used in
conventional SLR's for some time now). This built-in cleaning takes
place every time you power up the camera and can also be invoked from
the camera menu. It's reassuring to see at least one manufacturer
taking dust seriously and attempting to solve instead of avoiding the
issue.

Of course you could also mention Olympus hasn't adopted any IS
solution yet so it cuts both ways.
-Rich