Circlet of Shadows importance?

So I am new to playing SK, and I am wondering just how important the .1 cast time CoS is for the class?

I am happy to buy one if it is something I need, but if it is merely a luxury I will probably wait.

Is there some big reason to have this?

None?

You get Cloak of Shadows instant aa at 70 and it goes to permanent invis at 85.

You can buy a lot of instant invis potions for what it would cost in game for a Cloak of Shadows in the meantime.

It's quite useful for some classes on TLPs, but on Live it's just a prestige item.

This is TLP

If you get one as a drop it's great, if you are looking to buy one don't bother imho, very much over-priced as a rule.