If there's one thing time has proven it is that open source projects (usually) leave a lot to be desired in the UI department. UI is one of those things where a benevolent dictator is a good thing, it gives you consistency and given a talented designer leading the team gives you a far better product.
The typical path for for open source UIs seems to be to try to please everyone, which means making something that isn't great for most people who don't want to spend half a day customizing their interface.
To be clear, I wasn't actually thinking about 'design', more like, features. Perhaps you're right, and perhaps I'm longing more for some kind of plugin architecture.
Something along the lines of stable and opt-in unstable UI branches with frequent releases.