What timings are you experiencing/calling "performance hit"?
I have tried to pull a movie together showing the difference in speed between the Built In Preview and the Load Full Size images. At the end I have also swopped across to ViewNX so that one can get a speed comparison from there.
http://mikeandmorag.co.za/idImager/Load ... Speed.html
As you can see from the Video - when using load full size images - the process is considerably slower - and seems to "stall" every few images - resulting a quite a long delay.
On an individual basis it maybe doesn't seems so long (
D800 preview from a NEF displays within 1 sec
) but when you want to quickly scroll back (or forward) three or four images to do a quick comparison with the viewed image and then back to the viewed image it does take a long time to load and get there.
It seems as though ViewNX does some sort of "progressive" load of the images - but even then the time lag seems small - and one can quite quickly "zoom to 100%" after the image loads on the screen.
I hope that this helps you understand why I feel that the Load Full Size seems so slow or seems to lag behind my keystrokes.
Thanks for the tip re LightTable - that does make it quicker to view - now I just have to get my brain trained remember the Shortcut Key. Is there any reason why there are no "grey forward and back arrows" in the lighttable ? Would you consider it if I put a feature request in for them ?