I saw this old post, and wanted to add a few more thoughts.
Many seem to think that Lee filter always means ND grads or something like it.
Actually Lee makes some excellent solid ND's 0.9, 0.6 and 0.3. and if you are after a slower shutter speed, one of the best ways to achieve it is with a ND filter.
The 14-24, is an excellent lens, it has some issues, weight, and flare problems, but I would easily put the results from mine up against any of the Zeiss primes on either a D800 or D800E. My only issue has been the use of traditional filtering with this lens. As I prefer to work in and around water, I tend to always want a CL-PL on a lens. This adds yet another issue for the 14-24 as there is nothing in a normal filter that will work.
Lee with the SW-150, allows you to have both a 2mm and 4mm filter slot in mounted on the SW-150. You can purchase a 4mm CL-PL 6 x 6 that just fits the 4mm slot of the SW-150. In front of that you can add a 2mm ND filter. It takes a bit of work to get the 4mm and 2mm to fit, as the normal Lee screws are not long enough. However you can purchase machine screws that will fit. You still won't get any vignetting and if you use the back ground reflection guards, you have an excellent solution
Another filter to consider is the Singh-ray reverse Grad setup. These work a bit different than a normal ND grad as they have the strongest ND in the center and then fade back to the top. Great for a sunset, sunrise. The only issue with ND grads I have is that you have to watch foreground objects, trees especially that will be too dark since they are inside the reach of the grad.
One solution that really lets the 14-24 be my main lens on the Nikon's for landscape work.