Personally, I don't have a problem with multiple brands of a platform. In fact, its one of the reason I have always bought American. I look at it like this, you've got 3 or 4 choices of styling to attract someone. If I don't like the Chevy, maybe I like the Pontiac, etc. It's not the concept, but the execution that remains a problem. I actually think companies like GM are in better position now to offer this type of choice than in the past. If they rationalize which parts can and should be common and then focus on the differentiation parts, they can keep the costs down. The fact that so many parts have been reduced across the board already along with the technology aspects, means that it should be cheaper to execute this now than in the past. Really, how many door latch striker designs do they need? Or antennas? Or lug nuts?
I have always been disappointed in the choices available in Japanese cars in particular. The way options are bundled or available only on certain models has always turned me off. Unfortunately, I see the progress of this philosophy at GM on the new Malibu. Somehow a marketers idea of the ideal car and mine are always different.