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.
5DIII, 1DX, 8-15/4L, 16-35/2.8L II, 24-70/2.8L II, 70-200/2.8L II, 70-300/4-5.6L, 200-400/4L 1.4x, 17/4L TS-E, 24/3.5L TS-E II, 35/1.4 (Sigma), 85/1.2L II, 135/2L, 600/4L II