Temperature wise? I'm sure it will run hotter, but not that hot depending how much he OC it.
Overclocking the Athlon 64 3000+ to 2.2GHz can improve the performance by another 7-8%. It is not only higher CPU clock frequency that contributes to the performance improvement here, but also faster memory, higher working frequencies of HyperTransport and PCI-e buses.
*Fact: Microsoft Window's Blue Screen of Death vs Computerforums.org's White Screen of Death. Which is worse?