For "feature complete" I assume they mean that they've implemented all the stable features of the similar container in the standard library, I did not verify th

For "feature complete" I assume they mean that they've implemented all the stable features of the similar container in the standard library, I did not verify this but it seems like a reasonable understanding. You can reason about its safety/ correctness the same way as the stdlib container types and this will be true for all of (safe) Rust. The performance considerations have a new dimension for multi-threading though. In single threading you don't need to care whether doing similar operations "at the same time" could affect the performance of what you're doing, but in a concurrent system that's a consideration. Accordingly you would need to benchmark this carefully for your specific usage - just because it's correct doesn't mean it's fast or even acceptable.