Don't confuse Centrino with Celeron. The Centrino Duo will be a dual-core Pentium M (with a large 2MB L2 cache and 667 Mhz bus speed) and intel wireless
Adapter.
Celeron is essentially a low cost Pentium 4 that's been crippled in bus speed and Cache.
The technology behind the Pentium M(and likely to be pulled thru to the dual-core) avoids NetBurst architecture and HT tricks that the Pentium 4 needs to keep its dense pipelines full and provide decent performance at high clock speeds. A Pentium M with its large cache and less deep pipelines outperforms Pentium 4's at the same clock speed and also provides exceptional low power, low wattage performance, which reduces heat and increases battery life.
Centrino Duo is a win-win, especially in small form factors such as PowerBook\iBook\Mac Mini.