Well I decided to make the move. The price is too good to let it pass. What motivated my decision is that even if the writing speed of my SD cards is good, I find the playback speed on the lcd awful because of the size of the files. I saw a review that said this card really improved the browsing speed on the D800 and also that writing speed is substantially faster. They got me.
Another thing is that I couldnt use Eye-Fi anymore since the D800 only got one sd slot and its occupied with a memory card as of now. When I use it, I transfer jpg over Eye-Fi, but the camera also records in raw in the other slot. Not possible on the D800 when you got sd memory cards.
With my SD's, I was getting 15 shots under the 4fps continuous mode before buffer began to actually limit the fps. Which wasnt bad, but like I said the playback on the lcd is a pain. Cant wait to compare and see how much shots it takes before I fill the buffer with these ones and if the playback can be as instant as it is on my D7000.
I bought two since the second one was only $100 when you take the two pack. Lets just hope they will get back in stock soon. They say 3-7 days.