I tested FW4.0 with all my lenses (14mm, 23, 52, 18-55, 50-140) and it's great, I was able to focus while riding my bike, focus on fast moving people in dimmed light, nailed face focuses at 1.4 Fuji.. there's some good field test here http://www.francescovicenzi.eu/rally-against-closure-of-aboriginal-communities/