It does sound a lot like Cinnamon, though I confess to not knowing the details of the Gnome world.
Are there many functional differences between Mutter and Metacity? I do hope they share lots of code and generally work together; the only way these "we don't like the Gnome 3 interface paradigm" forks are likely to last is if they work together (and I'm glad they both sound like they are keen to ensure they work with upstream libraries etc).