I was lucky and could test this lens. It is very good and be used at full aperture. Normal pictures look great. AF is slow compared to mechanical ring-USM lenses.
Manual focus is only possible with camera power on and camera activated.
This is very annoying. Test target was a building 30m away. At 2.0 the EF 50 was very good. At 8 both EF 50 and Ricoh was excellent with the zoom almost as good. The vignetting was high at 1.0, mucher better at 1.4 and almost gone at 2.0.