As of 12/15/06 Monsoon's haste effect and FBSS haste effects DON'T STACK! The FBSS effect prevail, that makes Monsoon darn useless, as a combination of FBSS + 2h pristine imbued ebon sword or axe is a way better. I use PGT + pristine imbued ebon falcion +FBSS in DPS mode, in addition to faster haste than Monsoon and more DPS that gives me 2 more effects - Might of the Land from PGT and Gleaming Strike.
There are better swords out there but this one is excellent and easy to get. It's as good as most legendary swords in this level. Only fables are better.