Seen below, the new heatsink seems to have a smaller base but Intel claims there won't be any performance differences due to the design change. Cooler mounting will also be unaffected.
Intel will begin shipping Pentium, Celeron, Core 2 Duo and Core 2 Quad chips bundled with the updated cooler on January 31st (2011). The old heatsink will continue to be available until inventory is depleted.
Source: TC Mag