I wouldn't say it's bad. It's confusing at first, like most interfaces with a ton of controls, but you gradually get used to it and know where things are.

The bad thing about the UI at the moment for me is the lack of HiDPI support (as far as I can tell). And back when I was using OSX, the interface seemed a bit janky since it used XQuartz and it generally wasn't very native both in terms of UI rendering and its default keyboard shortcuts.