I can't think of anything that beats the dual hoverslam for cool factor. What a breathtaking sight! Mad props to Elon and the team at SpaceX for getting the hat trick.
Now it will be interesting to watch how "low cost" commercial heavy launch capabilities will be used. I know they are working hard on the the BFR but there is money to be made here that I'm sure at least Gwynn Shotwell is looking to take away from ULA and others.
Each booster generates 3 distinct "booms". IIRC the causes of each are slightly different, but it's nutty hearing it in person!
One is from the engine bell, one from the widest part of the body by the landing legs, and the third is the grid fins.