According to this article at Toms Hardware, a single Agena core is right around 13% faster than a single Windsor core, on average. This 13% figure represents the average difference between the cores tested in 18 games and apps, and exludes synthetic benchmarks. They didn't test Super Pi, but comparing my Phenom 9850 @ 3GHz with 3GHz Windsor scores on the internet, it appears that Agena is about 14-15% faster than Windsor in Super Pi. So with AMD processors, at least, it appears that improvements in Super Pi closely track improvements in games and apps.