Having owned both systems as well, I think a big reason you hear the nikon users complain is because the 70-200 VR I was such a stellar lens that it made for some very big shoes for the VR II to fill. The Canon 70-200 2.8 IS 1 was in my opinion kind of a dog (owned it, the old magic drain pipe, and an f4 L IS), while the L IS II was in a totally different league. Honestly they are both great lenses, but relatively the canon version was a much bigger improvement than the nikon.
The real laughable quote I heard the other day was someone saying the Canon 24-70 version 1 was better than the Nikon 24-70. Made me chuckle a bit.
As for this lens, I think the price is incredibly fair. People hear f4 and think it should be tons cheaper than the 2.8 and completely useless to pros because its not 2.8. Those people are idiots. The size and weight of an f4 lens in this range makes it incredible. I absolutely swore by my canon. Plus with 5 stop VR unless you are shooting sports or using an older body that can't handle anything above ISO 800 then you should be fine everywhere.
The real test will be the IQ though, the Canon has stunning IQ (not only sharpness it amazing color and contrast rendering).