In the last 8 days I have shot 3 weddings, 2 last weekend with pair of D700's and one yesterday with one D700 and my new D800.
I won't be editing images for a couple of weeks and as they mostly have people in I would not be able to post any here. But I will post some on my blog here: http://www.diamondphotography.org.uk/blog/ (in a few weeks)
To set the seen a little, the wedding was very fast paced, it was cold and damp so outdoor shots had to be done quickly to beat the looming rain.
I used 24-70 f2.8 on D800 and 50 f1.4g on D700.
What I would say is D800 definitely have more detail in most situations, but you have to zoom in to notice.
D800 performed well in good lighting but less well in church. Once you start hitting 800 ISO images start to look quite soft. These were on a tripod at around 100/s, f2.8. I compared similar situations for my last wedding and my first impressions are D700 was at least equal (if not a little better).
I liked having dual cards on D800, saved a lot of swapping.
Nikon have swapped zoom buttons, why I do not know but I was forever pressing wrong one!
One of the most frustrating things was the delay when wanting to view images. If I took a couple of shots then went to view them there was a definite delay (and I'm using 95MB/Sec card), probably only 1-2 secs but seemed like 5 when your rushed.
Overall I would say if you're looking for more detail then this is a great camera.
I have another wedding on Friday so will give another update then.