This price slide only makes sense. I guess they figured that the first wave of buyers who are ready to pay whatever for the "latest and greatest" is now depleting, the 800 is getting more in stock and its bugs are being taken care of, so its time to move on with getting the price down to the actual market value.
Canon could make a bigger splash in consumer world with original MSRP of MKIII under $3K, with MKII as an entry level body for another year and with $3800 high megapix model. Instead they decided to milk a certain consumer group and only after that to adjust the price. Disgusting but quite predictable corporate practice.
Personally, I'm waiting for the 800 price slide. Just a thought of having a 36MP body with high DR for studio work for around $2700 makes me hyper.
You won't see any difference in IQ among the D800, 5D Mark III, or 5D Mark II. You're paying for larger files is all. Especially so for studio/portrait work.