I have tested it on an EPL5, which I don't plan to use this lens on regularly because of the weight. but the EPL5 IBIS (same as EPM2's) handled it just fine I think. Sure I suppose it's not comparable to 5 axis but better than none, no sign of shutter shock problem yet. but that's just me, I'm using this lens on a G5 that doesn't have any IS and the only blur I seemed to get is OOF blur due to the thin DOF
It's been a long time, but the OIS on the 45-200 was noticeably better than the IS in my E-PM1. Don't know if that helps... you'll probably get two stops out of it, if I had to guess. That's a 1/80 shutter at the long end, not too bad.