I have one. I think it's an excellent lens- two main improvements would make it top-notch:
1) weather sealing (a piece of hair/long dust somehow got behind the rear element of mine while outside on a windy day- kind of aggravating but I can't seem to see it in pictures at least, so that's a relief)
2) slight IQ improvement/less purple fringing at 1.4 (at 1.8 and above it's great- peaking around 2.8 in my opinion)
Weather sealing was one of the main reason I did not get the existing model. I am anxious to see the new version annouced though! UNless the new 24-70 II is so good that it will make us forget about prime!
1DX, 24mm f1.4L II, 50mm f1.2L, 85mm f1.2L II, 135mm f2L, 24-70mm f2.8L II, 70-200mm f2.8L IS II : D800, D4, 24 1.4G, 35 1.4G, 50 1.4G, 85 1.4G, 24-70 2.8, 70-200 2.8 VR II