Upload & Sell: On
The first step is to get the lens focusing properly, then you can evaluate whether it has sharpness issues at f/2.8. I've found that focusing the 14-24mm on the D800 is extremely challenging, much more so than on the 12MP bodies I used my copy on prior to the D800. This is mostly due to the higher demands of 36MP, esp at the extreme corners/edges, but also due to a combination of focus shift on the lens between f/2.8 -> f/4.0+ plus the D800's LV implementation where the lens is always stopped down to the dialed-in aperture. Making matters more difficult is that when the 14-24mm is misfocused it produces all kinds of strange focus fields across the frame. It took me 300 actuations on my D800 to perfect focusing on the lens, and that was just at 14mm @ infinity!
I have a long thread about all of this here: http://forums.dpreview.com/forums/read.asp?forum=1021&message=42026957. I'll save you from having to read it and give you a quick summary on getting your combo focusing well:
* For phase-detect AF (through the viewfinder), a perfect AF tune value is essential. I tuned my lens at infinity because I almost always shoot at the lens's hyperfocal distance. I had to do a full-matrix of AF-tune values (in +/-5 stop increments) across all the aperture values to find an optimal set of values that work at both f/2.8 and then everything else.
* For contrast-defect AF (Live View), the process was complex but luckily you can achieve good focusing without having to reproduce all my leg work: If you intend to shoot at f/2.8, make sure you're focusing at f/2.8 (aperture set to f/2.8 in LV). If you inted to shoot at any other aperture, focus *only* at f/4.0, then change to desired aperture to take your photo (if it's different than f/4.0). This advice is necessary to work around the focus shift on this lens, which is most prominent at f/2.8 -> f/4.0.