Just bought 5D mark III - heard Nikon D800E is much better image Quality? did i make a mistake?

These are really good answers.  I'm pleased and proud of our forum members who have answered this potentially incendiary question fairly and without rancor. I love my D800E. It is without a doubt the finest camera I have ever owned. But, I agree with the previous posters. Both cameras (D800 and 5DIII) are superb. The advantages of the higher res available with the D800 will not compensate for the aggravation and financial loss of switching systems. In addition, while the newer Nikons have decent video capabilities, the 5DIII is still the better choice for all the video the OP seems to shoot. It seems we can have far more productive inter-brand discussions if people respond as they are in this thread.