While I assume Venges question to be completely rhetorical I will answer.
They provide nothing new under the current spectrum of things. If say Dwarves could not have any magic, and or bow, crossbows or in short any other distance attack then guns might be for them an equalizer of types.
Hell, even now we can argue that bows and crossbows are not necessary, but there is a feeling that they can be added quite well into the current game as a ?ranged melee attack? with disposable ammo. In most cases the target is at a loss of certain defenses, but in most cases the base damage would be lower for the ranged attacks?though in the right circumstances they would do roughly the same damage. In short it follows my philosophy of?the right tool for the right job.
Now, as for coolness factor?I see little that guns provide, just another area of weapons and alchemy. But add in questions like??if you are engulfed in flames and are carrying gunpowder, what happens to it??
In short, if we add chemically driven projectiles of any type, I would personally make them so dangerous to use that most people would not bother?making them pointless.
But, that is just my take, if anyone can add something that they add that would be really cool?then I would most likely reconsider.