I've extensively shot all three. My main workhorse camera though, was the D3s before migrating over to the D4.
I have to say that I am pleasantly surprised by the improved AF performance and color accuracy over the D3s. From subject tracking to color rendition in low light/high ISOs, the D4 is better than the D3s. Haven't had a chance to test out AF-C tracking since the latest D4 firmware upgrade, although I hear it's even better.
While not a monumental upgrade over the D3s, 16MP is plenty of real estate for most wedding, portrait or landscape applications.
Although the D800e is very capable of producing stunning mega-sized images, the AF and low light capability are nowhere close to that of the D4 (or D3s for that matter), so I think it struggles as a good "everything" camera. If you’re shooting mostly landscape, it’s a different story.
If they do come out with a D4x as rumored, it will combine the low-light, high speed AF performance of the D4 with the image size/landscape capabilities of a D800e. But for now, I find the D4 to be the best Nikon camera out there for multi-genre shooting applications. Of course, the D3s is awesome too, although the AF and color accuracy are improved in the D4 IMHO.
I think we’re getting closer to a camera that can handle it all – although I find the D4 to be extremely capable in everything I shoot, from landscape to PJ. I just can’t say that with the D800. Of course, the D4 is big and heavy – but like everything else in photography, it’s all about tradeoffs.