I've had these SSD's for about 6 months now. When I first installed them I was getting perfect readings. With the Write speed about 900 MB/s or so. I have done NOTHING to the SSD's since then. This is what my write speed is now.
Asus Maximus IV Extreme-Z
GTX 680's SLI
2x Samsung 840 Pro's in Raid 0
In case it is asked, the SSD's are correctly installed in the proper Intel ports on the motherboard.