I don't like to use the numbers to switch forms, it takes away from the game imho. I like using Naija as the hub between forms, the intermediary and in the heat of battle I like the *whump* of switching back to her and the frantic singing to switch to energy, beast, nature or whatever is needed. the tones of her form switching enhance the the background music and the energy blasts staccato nicely to the songs of battle.
I've only used number switching during Octopus prime and bubble jumping, places that are a freaking pain or need precision that I don't want to botch up.