I hate relying on battlefury cleave though, it's not going to work if the enemy isn't cramped up together, in which case maelstrom might be better since it has better AoE and is much cheaper? I wouldn't consider upgrading to Mjollnir though, because attack speed seems kind of a waste on Ember. So non battlefury build would be something like Phase, Maelstrom, Daedalus and then +damage items like MKB, Divine or maybe even a second Daedalus.
Then again if you have heroes on your team like Seer with his Vacuum or Magnus I would definitely stack Battlefuries, or if you're against someone like PL or Meepo. Not to mention you get good HP and mana regen (Ember needs mana) from all those Battlefuries.
Dunno. I guess in most cases Battlefury really is better even though you have to farm much more gold because it also scales while Maelstrom's chain lightning doesn't and falls off late.
Just thinking out loud.
Also, does Maelstrom proc if there is an active chain lightning currently hopping around? Because if it doesn't it basically means Maelstrom will only proc once per Sleight of Fist.