I'm curious about this too.
If I understand correctly, both the 955 and the 965 max out at the same level if overclocked. So if you plan to overclock, there's no need to buy the more expensive CPU. For that matter, if you're overclocking, wouldn't the 945 be a better choice? Of course, if you will not overclock, then the 965 makes more sense IMHO. That's what I've been able to gather so far from my reading.
Just my thoughts and not necessarily knowledgeable ones.
Peace.