That isn't all, actually. Using F/1.8 on M4/3 vs F/1.8 on FF is different.
symbiote28 - read this:
http://www.luminous-landscape.com/tutorials/understanding-series/dslr-mag.shtml
To add on, the difference in the Depth Of Field you get from f/1.8 on m4/3 vs Canon APS-C vs FF from a mathematical POV can be calculated from the DOF formula.
DOF = S[SUB]F[/SUB] - S[SUB]N[/SUB] = [ 2(m+1) * F-number * c ] / {m[SUP]2[/SUP] - [(F-number * c) / f][SUP]2[/SUP]}
Where
S[SUB]F[/SUB]= Furthest subject distance in focus
S[SUB]N[/SUB]= Nearest subject distance in focus
m= i/s = (image distance from lens to sensor) / (subject distance to lens)
F-number = f/D = focal length / aperture
c = circle of confusion for sensor ( use 0.015mm for olympus m4/3, 0.019mm for canon 7D APS-C, 0.030mm for canon 5D FF)
So as you can see, you can reduce DOF (more "bokeh") by increasing focal length(f) or decreasing the F-number(wider aperture)
Using the current example of FF equivalent 50mm at f/1.8 with the same picture composition at 5m from subject (after 1.6x and 2x "magnification" respectively), for
Canon 5D : using focal length of 50mm on lens and standing at a distance of 5m from the subject, the DOF is 1.4 meters
Canon 7D(APS-C) : using focal length of 31mm on lens and standing at a distance of 8m from the subject, the DOF is 8.66 meters
Olympus E-M1/5/10 (m4/3): using focal length of 25mm on lens and standing at a distance of 10m from the subject, the DOF is 10.57 meters
Which means that in general FF will have a smaller DOF and more "bokeh" than APS-C and m4/3 when using the same aperture setting and picture composition.
Anyway if you want to skip all these calculation, just download Simple DOF iPhone app to know the DOF that you will get for respective camera formats, focal length, and aperture size.