Sharp in the center even wide open, and very sharp from about f/2.8. Corners start getting sharp about f/5.6. One of the only Canon wide angles with sharp corners. Terrific colors & contrast, great bokeh.
Focuses quickly and decisively in low light - it's more accurate and much faster than the 50 f/1.4.
People often say this is overpriced compared to the 35/2, but in my opionion there is more difference between the 35/1.4 and 35/2 than between the 85/1.8 & 85/1.2.