The update brings six new dual-core Itaniums and a single-core unit to the 9100 series, along with a few new technologies such as better error detection and correction, better power management and a higher FSB. All in all, the CPUs are aimed exclusively at the enterprise so the former feature addition is likely to be the one they play up the most. While in the desktop realm you pretty much never concern yourself over CPU errata or potential bugs in the hardware, enterprise deployments might have a bit of a problem with CPUs that do bad math.
One thing that was not updated, however, was the manufacturing process. These CPUs are still relying on the 90nm fabs, and the 65nm Itaniums aren't expected for another year or more.