The fastest 65nm Core2Duo with 65W TDP was the 3.0GHz E6850, released in July 2007. The first batch of 45nm CPUs was released in January 2008, the fastest one being the 3.17GHz E8500. A whopping 6% clock speed improvement, though admittedly the cache size grew from 4MB to 6MB. Bus speed stayed the same. I doubt that resulted in a 30% performance improvement overall, 10-15% seems more likely.
They followed up with some significantly faster CPUs a few months later, and I suspect they will do so with Ivy Bridge, too.
