borisbg, I feel I did sound too negative.
There was a time I wanted a longer lens and Sigma came up with their twins. Having had a less good experience with a Tamron zoom, I don't want to try another, stupid, I know. So I ordered Sigma and while waiting 8 months until I got mine because a Nikon owner stepped out of his order, I got myself the 300/4 which is also fantastically light and small in size.
While that one was away for repair for nearly one month, Nikon service sent me a 80-400 as step in lens until they got the firmware and hardware to fix the flaws of 300. I don't know if I kept order up in case Nikon came out with that 200-500 with fixed aperture - in my eyes a benefit.
It's good to have choices. And it's good Sigma and Tamron are forcing Nikon to react, it's also good Sigma eventually got a bit kicked in the a... for their long time in between announcing and delivery. Hundreds of possible customers round the world were waiting for their 150-600 and patience isn't endless once you get new choices. So I hope for Sigma to be a little bit more careful. And for Nikon, too, because delaying the already announced delivery always has the laste of "something is wrong".
In Nikon's reputation there's this little "again!" coming up quite soon.
Supporting a comparatively small manufacturer has it's negative sides which I'm also experiencing in the place I work. We increased our portfolio of machines up to 4 new, in theory decreased the old machines but have to deliver support and documents for the old types as well, but we're still only two guys in my job. Times are a little more busy here.
Just found this comparison of the lens' size at Nikonrumors