Had a play about with the 24-70 f/4 IS today at a camera store. It feels a bit like a 24-105 but a bit more plasticky. The zoom ring felt quite stiff and didn't move smoothly, could be because its new but it had a courseness to it that i didnt like. There was no card in 6D test camera but from the preview screen the images looked quite sharp. IS was good down to 1/8th second at 70mm! Though i couldnt zoom in to the preview to check sharpness. Macro was fun, I can see this lens being quite popular with 6D users.