The swirley bokeh is not as pronounced on the APS-C sized sensor, since the FOV is cropped, but I assure you it is still there. The maximum effect is when you have a focus subject about 2-3 meters away and the background about 10-15 meters away, so count a factor 1:5 ratio for foreground/background subject distance. The optimal background is sunlit foliage. This is where you get that amazing special “cat-eye” effect.