I know this won't count... but, ive never been able to get anything I really liked using the Bubbles feature so I couldn't resist having a quick play with what David (DMerz III) discovered yesterday that you can plug .vdb files into the 'Bubbles' node density input.
So I generated a quick mushroom cloud VDB via C4D/XParticles, plugged it in and had a play.
Bubbles, for me, has now turned into a weird version of particle (static) advection and a mograph cloner. I hope they add VDB animation and custom shapes in the future.
Cheers
Peter