> Yes, but the upside is you avoid the complexity headaches of interfaces and covariance/contravariance and generics and all that stuff.

Maybe it's a matter of what you are accustomed to but not having explicit declared types gives me headaches. I find code without types horribly unreadable - because I can't see at the first glance what data a function processes, etc.

Also dynamic typing and its runtime type checking gives me that uncanny feeling of "something might be wrong but I won't find out till I hit it".