If you expect upcoming Intel Core 2 Duo processors based on 45nm process technology to be good overclockers, there's a good chance you're right. The guys at Chinese site Expreview have nabbed a 45nm Core 2 Duo E8400 engineering sample, and they've both benchmarked it and overclocked the bejeezus out of it.
By default, the Core 2 Duo E8400 runs at a stock speed of 3GHz with 6MB of shared L2 cache and a 1333MHz front-side bus. At that speed, Expreview's benchmarks show the chip performing 3% better on average than the existing 3GHz Core 2 Duo E6850. The biggest difference is in the TMPGEnc video encoder (8.47%) and the smallest in the Unreal Tournament 3 demo (0.1%). Nothing surprising there, especially if you've already had a look at our review of the 45nm Core 2 Extreme QX9650.
Things become more exciting in the overclocking section, where Expreview says it was able to push the E8400 to a stable clock speed of 4GHz with a 1999MHz front-side bus. That overclock apparently required a jump in voltage from 1.224V to 1.472V, but only increased the CPU temperature from 33°C to 46°C under load—still well within reasonable bounds—using a large copper and aluminum cooler.