Hasselblad X1D + Hasselblad XCD 21mm f/4 Aperture Series: Rock Creek, Upstream View
See my Hasselblad medium format wish list.
This series looks at performance with the Hasselblad XCD 21mm f/4 when focused in the distance. It gives a particularly good idea of corner performance as well as depth of field and just how important it is to choose the best focus.
Hasselblad XCD 21mm f/4 Aperture Series: Rock Creek, Upstream View
Includes images up to full camera resolution from f/4 through f/11.
This is the kind of performance I can get very excited about on a large sensor. If my budget allowed (for camera and lens), the 21m f/4 would be my #1 pick for the X1D because wide angle lenses this good are not easy to come by, particularly on medium format. My reference points are lenses such as the Zeiss Milvus 18mm f/2.8 Distagon and the Zeiss Batis 18mm f/2.8 Distagon and the Sigma 14-24mm f/2.8 DG HSM Art (all 35mm format lenses).
See my Hasselblad X1D wishlist.

Hasselblad X1D + Hasselblad XCD 21mm f/4 @ 18mm equiv (21mm) ENV: Rock Creek, altitude 9950 ft / 3033 m
focus at center
[low-res image for bot]