This is a very sharp lens. The focal length works very well on a 5D, but a little too long on a crop sensor. The bokeh is beautiful due to large aperture and long focal length. Colors and contrast are great too.
The drawback is that this lens need very good technique to perform well in low light when the shutter speed is low. Because the DOF is thin when wide open, you need a steady hand to get sharp results.
I give it a 9/10 build quality because it is not weather seal. There is no rubber ring at the lens mount area.