I don´t like the plastic body of the lens.
Me neither, same thing with the 100L - but was Canon seriously thinking about releasing a metal body, or are they set on releasing plastic lenses from now on?
I had the same thought when it was released, but after I had used it for a while I realized that it is a very solid body. High quality plastic does have some advantages also.
1DXII, 5DIV, 5DSR, 8-15/4L, 11-24/4L, 16-35/2.8L III, 24-70/28L II, 70-200/2.8L IS II, 100-400/4.5-5.6L IS II, 200-400/4L IS 1.4x, 24/4L TS-E, 35/1.4L II, 100/2.8L IS Macro, 300/2.8L IS II, 600/4L IS II, Profoto B1