Saudi Succession Rules

Back when Saudi Arabia proposed its new succession rules, I didn't understand what the big deal was. Apparently the "reform" is that it curtails the king's absolute power in that area. This might be true in a legal sense, but did the kings ever have practical power in absolute terms? I'm not sure, but I'd always been under the impression they had to be careful to balance the interests and ambitions of all the princes, many of whom have their own power bases. After all, even though Abdullah was the de facto ruler for several years before his formal accession there was still talk that he might not take the throne smoothly.