Since we already got GetAttackSpeed() function in current API I'm wondering why there is no GetBaseAttackSpeed() function as well? It seem that the only purpose for GetAttakSpeed() existence is it's usage inside some Damage Per Second calculators. And it would be cool great function but there's one small problem - to calculate such thing like hero DPS we need something more than just his Bonus Attack Speed - we need his BASIC attack speed.
Of course, developers can use some libraries or their own tables with listed heroes base attack speed but it's both unfriendly and irritating when it comes to updating our scripts every patch. We already got GetBaseDamage() function, so I think there's nothing on the way to implement GetBaseAttackSpeed() as well.