My ‘Big Shuriken’ arrived yesterday. The installation was painless if a little fiddly. The large overhang of the heatsink and its proximity to the PSU made attaching the locking mechanism difficult and the same for the fan headers.
However the proof is in the pudding. Running Handbrake with the stock cooler would cause my machine to overheat and shutdown within a couple of minutes. With the Big Shuriken installed the highest I saw was 68C.