The Samsung is a good one to go for if you are looking for speed. However, also make sure that you are using the correct SATA 3 port on your mobo (the intel one), that AHCI is enabled in BIOS and that TRIM is also enabled, and your chipset drivers are up to date. All these will help speed issues.
Correct SATA 3 port? Here is a picture of my motherboard http://www.gigabyte.com/fileupload/product/2/4489/8010_big.jpg,
the one I put it in was SATA 3 , is this the right port? I first got speeds of 470mb/s read and 170 write but these dropped to 420mb/s and 140mb/s after 13 days.