I own samsung laptop rf511-02 which comes with 4gb ram manufactured by samsung. Just to avoid any potential errors caused by adding new memory to the empty slot, I decided to buy Samsung memory. They were both in CAL of 9 and I have not yet had any problem with installing new one.
The windows 7 experience index went up from 5.9 to 7.6 (memory section) and I am very satisfied with it.
I did not want to rate feature and design but I had to in order to submit this review.