>>47
Defining sub-languages and using these features increases software complexity. You're adding to what a coder needs to know to implement new features or change something, which reduces productivity. Besides, I don't know how nice SML is otherwise (I'll look into it later since you recommend it), but I've seen LISP, and man, that's a sucky syntax (or lack of). Unholy amount of parenthesis and prefix notation makes programs harder and slower to write, and much harder to read and understand. I'm not talking about writing my own sysadmin hacks, but an application I'm getting paid for and I have to document.
>>48
Depends on what do you want to use it for. Macros in a word processor? Anything will be fine. IA in a game? I would care.