I wonder how many people choose which camera brand they'll buy based on the flash system. My guess is not many. People choose one brand or another based on a variety of factors, and the details of the flash metering system are generally quite a ways down the list.
Neil wisely points out that no matter what system you have, it's important to familiarize yourself with how it responds to a variety of conditions. Even within the current Canon system we have at least four different flavors of automatic flash metering - Evaluative, Average, Spot (FEL), and traditional auto (external metering) with the 580EX II. There are vast differences in how the system behaves with each of these modes.
Regardless of brand, regardless of mode, predictable results can be obtained only by gaining a familiarity with the system that comes only through significant practice.