From the press release:
The EF 40mm f/2.8 STM is Canon’s first EF pancake lens with a fixed focal length of 40mm and wide f/2.8 aperture, making it ideal for photographers who want a versatile, compact and lightweight lens for portrait, reportage, travel or landscape situations. Precision control over the circular, seven-blade aperture is enabled by the EMD, producing a beautiful bokeh effect and an aspheric lens with Super spectra coatings ensures optimal image quality from the centre of the lens to the periphery for stunning shots of practically any subject.
Canon’s lenses—particularly the lower-priced models—tend to be hit-or-miss. If this delivers decent image quality, it may be my next lens.