Storm Cloud - Can it be useful?

It would seem like a good early weapon but Silverbranch still seems much better.

Does anyone know of any use for Storm Cloud, or is it just a unique for the sake of having one?

Maybe for EE Explosive arrow builds, you only need speed and some element other than fire on your weapon. Also, you usually have a lot of elemental damage passives but few physical passives being a templar or mara which are most commonly used for that build. Qillrain would ultimately be a better choice for EE, maybe it would work for elemental hit, but you can get much better bows for that as well.

Well, many uniques are just a levelling tool, nothing more to them.

Stormcloud can get up to 1.8aspd. That's the best aspd of any bow in the game that doesn't give 50% less damage. (Best equal with Lioneye's.)

Silverbranch is only good because of its 10 mana gained on kill. Its other stats are terrible. Just use one of these instead once you can wear stormcloud:

I use it to level very fast from level 10 to level 21 in :

Coves
Forest
Fellshrines

I'm finding it an absolute blast to use. I use it on a Shadow, focusing exclusively on attack speed, critical strike, lightning damage and elemental attack damage, and so far I'm tearing up with it.

I found a Malachai's Simula (Unique Iron Mask, has Blood Magic and +20% Lightning Damage), and I use a multiple projectile forking Lightning Arrow, and that's pretty much all you need. Lots of quicksilver potions and away you go. I really don't know how high the cieling can go, but I'm imagining fairly high.