Well...I'm not even considering buying an FX body, but, here's my two-cents worth.
1. I do macro, almost exclusively. Therefore, I really like the "crop factor" on my D300. My 70-180 Micro Nikkor is now an approximate 105-270 zoom.
2. As to the discussion of focus points...51 points lets me target my subject more precisely than 39 will. In other words I can frame my subject and then if needed "jump around" the 51 points to get the exact point of focus I want without having to move the framing and them move it back. Some will say auto focus for macro is not needed...well...sometimes it works for me and my "old tired eyes". Granted manual focus is my most used method.
I am one of those who is waiting (hopefully not in vain) on a D300 replacement.