Fisheye Anyone? What's a fisheye lens good for and is it worth getting one?

This isn't my first fisheye lens but, on APS-C, it's a very different experience compared to the same focal length on micro four thirds.
Fisheye photos from a Canon EOS M6 with a Brightin Star 7.5mm f2.8 lens.
Video filmed (mainly) on an Olympus E-M1 mk ii with 12-40 f2.8 Pro lens.