My main interest in NLL is its effect on compile times. Things have improved a lot recently, but the current numbers are still making me nervous.
The compiler has gotten substantially faster recently. It would be very disheartening if those improvements were undone (or worse) by NLL’s landing. I am particularly concerned that the pressure to get NLL into the Rust 2018 Edition could mean that performance regressions might be considered acceptable that otherwise would not.