Well so far I've hit 2.7 on 1.40 volts on the stock cooler. The memory becomes more unstable as CPU speed increases, even when I keep adding dividers. At 2.0 ghz the memory is stable at 200mhz, but at 2.7ghz, my memory becomes unstable unless I knock it down below 200... Currently the memory speed is at 180 mhz. So until I get better memory (not soon) I don't think I'm getting much more out of this. However, I am switching motherboards next week, and maybe the memory will be more stable on a new board.
I think with more voltage and a good cooler, there might be 2.9 in this chip.