There's a wiki page on Sandy Bridge.http://en.wikipedia.org/wiki/Intel_Sandy_Bridge_(microarchitecture)
Seems intel is going for more memory bandwidth, I don't know what 4x1600mhz will really do if were already not seeing much benefit from going above 3x1333mhz. It's wiki, so that might not be true.
The stock clocks are also higher then Nehelem, this could mean that we have even better overclockers coming. It even uses turbo mode to go to 3.8ghz! Hope that's true.
I would probably wait for the new arch since it will be a bigger leap then just a die shrink.