I recently got my first full frame camera, the Nikon D610, and a Tokina 16-28mm f/2.8. I have to admit that although I like the Tokina 16-28 f/2.8 a lot, I was a little frustrated with the soft corners when shooting wide open at f/2.8 even though it's freakin' fantastic and sharp at f/4.
I saw a "like new" Nikkor 14-24mm f/2.8 for US$1300 (it's usually almost US$2000), and in a late night impulse, jumped on it. I just got it. It came in a large box that was so well padded that I'm pretty sure I could have flung this off a two story building and the lens would be fine. I decided not to test that out.
I did, however, test out the lens just a few minutes ago.
The lens is basically like new, as they said. No scratches, no nothing. It's in really great shape. I ran out to my back yard and took some photos with the "like new" 14-24mm wide open at f/2.8. Holy CRUD. This thing is really sharp at the edges. It's barely softer at the edges than it is in the center. I did not do a direct comparison, trying to do the same shots in a star test as the Tokina 16-28mm f/2.8, but eyeballing it, I can tell you that I have never gotten shots this sharp on the edges (corners) with the Tokina at f/2.8. I totally get why people are raving about this lens.
The Tokina is seriously fantastic for US$625. I'm comparing it to a lens that costs almost US$2000, not a fair comparison. But the Tokina cannot produce corners this sharp at f/2.8. Neither can the Tokina 11-16mm f/2.8. I realize this is not a scientific comparison, but on the other hand, I know what I am seeing. At f/4, I believe the Tokina 16-28mm and Nikkor 14-24mm are very comparable across the entire image, but not at f/2.8.
This summer is going to be a LOT of fun! It's a little bit of a challenge running around during the summer with new equipment that I'm not completely familiar with and operating the equipment in the dark doing night sky photos, but I think I'll be fine all the same.