Hi Russel, yep, it's interesting to compare anti dust systems because many of them are far from infallible.
As you say, I've found the Olympus system to be most effective, although as discussed in the E-400 review, this may be as much to do with the relatively large distance between the sensor and the filter, than it is to the filter shaking the particles off.
Here's the page with our own tests and findings:
http://www.cameralabs.com/reviews/Olymp ... ge3d.shtml
Either way, I've had to go to ridiculous degrees to spot dust on an E-Series DSLR, whereas it's been quite appartent on my Canon and Sony samples to name just two. Maybe I live in a dusty place though!