With MFT sensors, sharpness isn't going to hold up past f/11
But that's the same DOF as f/22 with a Full Frame camera, and the Full Frame camera is going to have exactly the same diffraction problems holding up past f/22.
The only real drawback I can see with MFT sensors is extremely shallow DOF shooting, where there is no MFT DOF equivalent to a f/1.4 or f/1.2 lens on a Full Frame camera.