Besides, does Nikon actually call it a "pro" lens? I don't think they make that distinction for the customer with a special designation, unlike Canon.
THey put a gold ring on it so that the "mine's better than yours" fanboys can feel good about dropping $1200+ on it. Every time I've said it was marginal on DPR, I've been flooded by fanboys who own the lens and think it's the best lens ever- when I point out that I own one and compare it directly to a true professional lens, then they just whine about the price of the prime.
The Canon 100-400IS is slightly better at the long end than the Nikkor, but anyone who's seen the Luminous Landscape's 100-400 vs 400/5.6 test can see the difference between a "good" and "very good" lens- I owned a Sigma 50-500 which was sharper at 500mm than the Nikon 80-400 was at 400mm, but I never got to compare it to the Canon 100-400.
Both the Canon and Nikon f/2.8 prime 400's spank most everything else supertele except perhaps the 300mm f/2.8 primes. Even with a 1.4x TC, my 400mm @560mm is pretty equal to the 600mm prime in terms of sharpness, and I think it's sharper than the 80-400 with my 1.7x on it- though that may just be bias, I haven't actually done that comparison yet (the 80-400 stays lent out to friends.)
Paul