The new Core i7 965 is a formidable chip out performing the QX9650 in every area of the benchmark testing. However a cautionary note is that the i7 uses the faster DDR3 rams and this allows for a higher RAM frequency.
Overclocking the Core i7 965 has a variety of new options to tweak like, QPI frequency and other voltages. This gives the end user more settings to tweak and master where you may be able to squeeze even more out the the Core i7 965.
Reaching 4.0GHz was easily accomplished by either processor but since there is familiarity with the QX9650 we need to take our time exploring and familiarising ourselves with the BIOS options. A simply detail like 'multiplier' needed to be accounted for and is known as 'ratio' for the Core i7 965.
If you were to purchase a new setup today the new Core i7 965 setup would be preferred over the older QX9650 but this conclusion is based solely on a synthetic benchmark. We have yet to see and experience real world usage on a long term basis. Stay tuned as we continue to put the Core i7 965 through additional tests.