It might be good for the customer at first. In the long term, though, it's not difficult to imagine cheap -> free -> monoculture -> square one.

IOW it's good for the customer right up until the One True Product is shut down, or there's no viable business model anymore.

I'm not sure how an open monoculture is square one. If it becomes less than ideal to anyone, they can just fork it. Plus, you can't really shut down an open "One True Product" if someone can just use the open materials to start it up again.

The risk seems to be more in the camp of the company. If it's open, someone could undercut them more easily than if it was closed. So the onus is placed more on the ability of the company to continually add value through services or the kind of innovation that led to the product in the first place, rather than just protecting their IP.