Here you go:http://www.canonrumors.com/forum/index.php?topic=2933.0
The IS module is prone to give grinding noise and crap out in 1-2 years.
And call me extremely unlucky, my copy brought from overseas exhibits uneven sharpness/CA across the frame. The right hand side of the frame was blurrier and had more literal CA than the left hand side. The boken is also asymmetrical to the right side. So in essence it is de-centered from factory. Putting it on 1.4x extender gives VERY bad results.
In the end I took apart the lens myself and re-aligned the movable elements. It is in top conditional now and I am happy about it all around.
The rear group is critical to the sharpness of this lens and it is fixed by 3 screws with big screw hole for aligment and a dab of black glue. Not a very robust way to fix a critical group. All the rest of 3 adjustable groups have eccentric screws and can be adjusted precisely.
It took me almost 5 days to position the rear group in a good alignment and once that is done, micro-adjust the other groups and got very sharp image across the frame. Also with 1.4x is it very sharp.
So yes, I have went through horror with this lens but in the end I still like it