I have to agree and disagree with what everyone has said.
Yes this is a fantastic weapon for a Rogue who doens't have the Ragebringer. Keyword in that sentence was ROGUE. I had the Fungusbeast Spine and I backstabbed for about 350, with the R.S.P.F. I maxed out my backstab in PoI at 447.
Yes it's a slow weapon, but the backstab button still pops when it pops. Pre-Epic this is the hands down best weapon if you want hellatious backstabs.
If you are a warrior or a shammy, this things stinks.
The Fungusbeast spine (13/28 +2 disease) is very nice, but you have to understand that there is the possibility of a resist, so you aren't always getting that 15 damage.
Speaking from a rogue who has used it, it rocks, I can't wait till I get the epic to have the juicy stats to go along with the big backstabs.
P.S. you hit a mob for 450, it turns around to see what did it LOL