Is there much difference in performance between a ddr2-667 ram and ddr2-800?

And anyone of you are using Samsung ddr2-800 rams? I've never heard of them until now. How is their performance like? I took a quick glance of the chips at the shop and i couldn't locate the 'SAMGSUNG' word...just the model number...i wonder what chips they are using.

Those Samsung rams costs rm220 for a 512mb stick. They were recommended to me by the shopkeeper when i was about to select a pair of KVR ddr2-667 rams. I'll be using them on a C2D e6300.