The lens delivers the most intense effect when used on a full-frame camera -- I tested it with the Sony A7 II -- when there's a lot of foreground/background separation between the subject, a relatively detailed background and with the aperture wide open at f2.5.
It's a snap to get nice background effects for portraits with the lens -- those are sequins in the background (photo is retouched and cropped).
The one problem with manual focus is that I would have needed three hands to get the balloon to remain still while focusing.
One of the effects of the lens is to increase contrast, which saturates colors nicely.
When there's no detailed background, the lens still produces interesting color and contrast effects as well as vignetting.
As you make the aperture smaller, the effect lessens significantly and becomes a lot less interesting. You still get vignetting, though.
It posterizes some flat colors, like the sky.
The edge distortions swirl lights in interesting ways.
When highlights appear close to the center of the image, the 12-bladed lens aperture delivers lovely round results.
There's a lot less of an effect on an APS-C camera, like the Sony A6300 I used to shoot this -- because the combination of the long focal-length lens and smaller sensor decrease the field of view as well as increase the amount of area that's in focus. Still, it can produce nice highlights and smooth out-of-focus areas.
Another example of the effect on a smaller-sensor camera, shot at maximum aperture.
You can add an extra layer of creativity by using an in-camera filter, such as Sony's Illustration effect, in conjunction with the lens.
Shooting monochrome with the lens is a nice way to deal with low-light situations.
The lens' chromatic aberration is one of its charms.
The rest are just some more photo samples.