Usually, the biggest benefits we see from moving to smaller processes on short term scale is reduced power consumption, providing better cooled systems or longer battery life in mobiles. While eventually it all ends up benefiting performance, it seems with 45nm Intel has chosen performance as their primary goal. Intel's newer 45nm-based parts will all be receiving boosts to their L2 cache over their predecessors, with dual-core chips having up to 6MB and quad-cores up to 12MB. Also, the quad-cores will available at 3GHz and higher, in stark contrast to their existing quad-core lines which are often sub-2GHz.
Why would they focus on performance as a primary goal? Given that they already have extensive emphasis on power savings in other areas and that Core has been around for a while, they might be fearful of AMD making a comeback with their late-to-the-game architecture revision. Either way, it's slightly disappointing to see the power figures on the faster 45nm parts. Some, such as the desktop quad-cores, will still approach or possibly exceed 130W, the point at which the Prescotts really had issues.