Developer from Mozilla considered to write Heka - a server software to collect data - in Rust. But they decided that this language was not ready yet, so developed it in Go instead
quote from a developer comment:
I heard that Rust is quite complex already. For example it has four different types of pointers!@Mateusz: Yes, in fact, we did take a look at Rust. And, were Rust farther along, we might have ended up using it, it would be a good choice. But Rust is still evolving a bit too rapidly for production software, and the tools aren’t as developed. I think Rust is an exciting project with a lot to offer, but it’s not quite ready for most uses.
other Rust programs:
https://github.com/Jeaye/q3 - a Quake III clone in development
https://github.com/pcwalton/sprocketnes - NES emulator