My Megahalems arrived today and I put it on after work. Temps are WAY cooler than the stock POS cooler managed. My ram has high heat sinks, so east-west orientation is out. I stuck it on north - south (standard way) and not only does it fit, but it could mount a pair of 38mm fans in push - pull!
The 60mm fan I got to replace my dead NB fan is slightly too thick for the screws to mount it, and it would conflict with the Megahalems. Zip ties are a wonderful thing, and the heat pipes are a handy mounting point.
NB temps down by 20c with fsb (still) @ 1333. Have CPU @ 1.4v, 3837MHz at the moment, cool (mid 40's @ load but not prime stable yet. Will try a bit more juice...