I loved this spell and played lots of characters that use it. It is equivalent to wielding a weapon, but at the skill dp cost of directed spell, and it works with ANY WEAPON. So first, a nightblade can pick up just about anything and use it. Secondly, its cheaper than buying a weapon (if memory servers) Development point wise. Third, Certain character types (the highly disciplined + agile) will have be able to really shine in combat, without needing to be strong, or whatnot, for at least as long as they can power the effect. Fourth: its great for the improvisational weapon or when you have to scrounge something for combat.
The bar roll adds some randomness but if you have any background/special bonus to bar, this kicks the bonus into high gear.
The BEST though was the occasional pure spell user that got ahold of this list. Sure, the archmage can only wield the sword like a master until he runs out of power points, but usually that takes a while with a first level spell.