I occasionally think of adding lazy evaluation to Arc. I could make news.arc about 5 lines shorter if I had it. It could be that there are other types of code where it would make a more significant difference, though.
The biggest benefit of having it would probably turn out to be being able to say Arc has it in conversations like this. That might be a bigger deal than it seems, although I feel dirty suggesting the "nitpick preemption" philosophy of language design.
This is a significant psychological point that comes up in a lot of different contexts (sales contexts, mostly). But in the programming language context, I think it's a symptom of the dysfunction that the vast majority of discussions are at a superficial level (code snippets and theoretical features) and have little to do with building real systems over time.
That's true, although before we get too smug about those "out of touch with the realities of building software systems" academics, we should remember that often those seemingly absurd and fanciful little corners turn out to be serious game changers. Lisp itself, for instance.