Gradual typing does not seem to work very well. It requires a runtime check every time you pass data from a "dynamically-typed" to a "statically-typed" part of

Gradual typing does not seem to work very well. It requires a runtime check every time you pass data from a "dynamically-typed" to a "statically-typed" part of the program, and then a conversion step from statically-typed to tagged data for the converse. These things eat into performance, in the end it's no better than what dynamic types would give you, and a lot worse than what one could achieve with static types.