It is a great tip. I didn't know you could hold your finger down on a symbol and return swiftly to the regular keyboard.
But it's not enough. There is plenty of GUI room for the commonly used symbols to not have to toggle in the first place.
And like someone else said, you should be able to customize your keyboard for what you're trying to accomplish. Programming, writing a novel, chatting, etc, all could be customized to increase efficiency.