Compared to Bulldozer there already is a nice collection of benchmark numbers for Sandy Bridge. For example those posted by Coolaler, a few BOINC benchmark results and a video with a mobile Sandy Bridge running Cinema 4D. The video analysis done in the Planet3DNow forums resulted in a deciphered score of 19641, confirmed by the measured run time (44 s). This means, the tested mobile Sandy Bridge processor was as fast as a Core i7-975 Extreme. Another comparison could be done by using a recently published Geekbench result of a 1.6 GHz Sandy Bridge CPU. So I compared it to a Core i7 also running at 1.6 GHz and made following table with overall results and a diagram showing the differences in detail.

So the average performance increase with those CPUs at the same base clock, but with different Turbo Boost implementations,  is about 20%. In the diagram below we can see a significant average difference in multi-threaded benchmarks: