>In my Overton Window herbceptions are already in the standard and
>everybody is happy about their performance. Wishful thinking, I know.
>But we'll see.

I think there is a consideration against defaulting to exceptions where none of this stuff matters because it's a fundamental problem agnostic of any implementation: defaulting to exceptions on things that are likely to deal with external input is defaulting to the creation of denial-of-service vulnerabilities.