The final draft made an effort to address those concerns -- but also they are completely inapplicable to optimized builds, as kibwen points out. (And if you care how fast your code runs, you really do want optimizations...)

AFAICS these concerns apply even to optimized builds unless they are also "ndebug", right?

The nightlies are built with optimizations. And trust me, nobody's going to be distributing Rust binaries that weren't built with optimizations because Rust code built without optimizations has performance on par with Ruby rather than C++ (LLVM's optimization passes do a hell of a good job).

Ah sorry, my mistake. I think I had optimized builds confused with "ndebug" builds. But it sounds like only ndebug builds disable overflow checks, and Rust nightlies don't use ndebug.

There's a discussion going on right now about whether the Rust compiler should optimize by default:

http://internals.rust-lang.org/t/optimizing-by-default/1532

thestinger seems to have a kernel hacker or embedded systems attitude, which is probably lower than 1% of all use cases; that's not to say it's not important, but he's generated an unproportional amount of, let's say, loud signal.