Dual-core Sandy Bridge mobile is expected to give 20% higher performance than Arrandale, at least when comparing the high-end models of each line.Geekbench scores have already proven that the 2.13 GHz i3 is equivalent to the 2.4 GHz Core 2 Duo and the higher clocked 2.26 i3 is equivalent to the 2.66 GHz Core 2 Duo.
So no, there won't be a performance boost until Intel bumps up the GHz in 2011. Nice try though.