Serious D800 / 800E Questions Before I Buy!

Forgot to mention... I tried the D600 and ended up returning it.  I didn't like the build quality all that much (very equal to my D7000) and I also believe that I might have had a flaky D600 - it was VERY sluggish in operation...very slow writing to the card/accessing playback, and I would often seemingly fill the buffer after shooting only 4 or 5 shots.

That seems to me like something was goofy with the D600.