I find that in general overclocking is not worth the loss of stability for the minimal performance gain. Now before you jump all over me I am not talking about a uber setup with a good cooling system and a correct ratio so no bottlenecks occur. Even with those setups you could probably use the money you tweaked your overclocking setup to just buy a new faster cpu or graphics chip. Overclocking is more of a hobby than a worthwile speed tweak.