Fil-C has advanced a lot since I last looked at it:

> Fil-C is currently 1.5x slower than normal C in good cases, and about 4x slower in the worst cases.

with room for optimization still. Compatibility has improved massively too, due to big changes to how it works. The early versions were kind of toys, but if Filip's claims about the current version hold up then this is starting to look like a very useful bit of kit. And he has the kind of background that means we should take this seriously. There's a LOT of use cases for taking stuff written in C and eliminating memory safety issues for only a 50% slowdown.