In general Rust is fast but slower then C: "Rust is safe indeed but, unfortunately, far from fast. By the moment of writing this article, it is comparable to Java, Go, and Haskell regarding performance" http://www.viva64.com/en/b/0324/
Also, microbenchmarks are usually not very good at representing the real world characteristics. But then again, please look at the current version of the linked benchmark.[3] Rust now positions itself in the second place, thanks to the recent improvements given to the Rust programs used in the benchmarks. I believe Rust isn't as fast as highly optimized C, but I think it is safe to say that Rust is just as fast as C++, and both Rust and C++ are much faster than GC'ed languages such as Java, Haskell, and Go.
Edit: I would even say that if Rust's performance is comparable to GC'ed languages, there's no point in using Rust in the first place. Rust is paying a lot of complexity to achieve memory safety without relying on garbage collection.
[1] https://news.ycombinator.com/item?id=9531822
[2] https://www.reddit.com/r/cpp/comments/35pn6h/criticizing_the...
[3] http://benchmarksgame.alioth.debian.org/u64q/which-programs-...
Rust has a lot of nice safety features not related to memory management that I'd love to see even in a language with GC. On top of the obvious lack of data races, linear types and borrowing are great for ensuring other kinds of sanity like preventing you from mutating a collection while you iterate over it.
I'm not sure that's a fair assessment.
Even if you didn't gain anything in terms of raw performance, the gains in performance predictability would probably still be enough for many applications.
Even if you didn't gain anything in terms of performance at all, the ownership semantics also give you good safety characteristics around concurrency, which would still probably be worthwhile for at least some applications.
That said, I want safety more than speed. Speed I can get by writing an unsafe extension in C/C++. Safety is very hard to achieve in C/C++. Getting it right is the first priority. That's why I see Rust being used instead of where traditionally C++ is the default. Or some other new language that can fill C++'s shoes. Rust does seem like the strongest candidate at this point.
I'm confident Rust and Golang performance will improve as the projects get more mature. The generated code is full of optimization opportunities.
[1]: Autovectorization optimizations by C++ compilers tend to be fragile, small changes will undo them. So far easier to use intrinsics than figure out the black magic for autovectorization optimizations.
Using 1.4 since 3pm PDT yesterday.