Right now, I have the best of both worlds. I had been shooting a D200 and D300 when I had the opportunity to buy a D700 with MB-D10 and 5 batteries for $1500 just about 2 months ago now. And it was in new condition with only 1700 actuations. Needless to say I sold the D200 and purchased the D700. I now have the MB-D10, which can be used with either camera and allow 8fps with either. As others have stated, I have tended to shoot more with the D700 since I got it(new (to me) camera syndrome). I still use the D300 (bought new in Feb, 2008 and has about 9000 clicks on it) when I want to reach out there, birding and wildlife or macro. When I'm taking pictures at parties or in the bar, I'll grab the D700 for low light and also for the relatively wider field of view.
I realize not everyone can go with two bodies, but the ability to pick up either of these two and be instantly familiar with 99% of the controls is fantastic. They are almost identical in ergonomics and control layout.
The picture quality of either of these cameras is excellent and it will be quite some time before I feel I have a need to upgrade as both of these cameras take wonderful photos even when placed side by side with anything out there today by either Nikon or Canon.
Just color me happy.
Kim
Western burbs of Chicago