Image quality results have been added to the Canon EF 50mm f/1.8 STM Lens review page.
We know that this lens has the same optics as the Canon EF 50mm f/1.8 II Lens. Here is the Canon 50mm f/1.8 STM compared to the 50mm f/1.8 II.
Look at this lens' image quality at f/4 and then look at the price tag. Very nice.
B&H has the Canon EF 50mm f/1.8 STM Lens in stock.