Rust compiler/stdlib are incredibly solid. Unfortunately, tantivy works with nightly and I hit a bug in the compiler (my code would segfault sporadically). I wasn't really sure the bug was in the compiler, so I shared my problem on reddit, someone else experience a similar issue and ended up filling the issue. It was solved in around a week.
The second issue was a 10x-slower performance regression. I didn't report it, because I suspect it is due to inlining, and I was asking too much to the compiler to begin with. Still, a 10x performance change is unexpected.
Apart from that I hit a major issue in crossbeam (memory-leak) that was already reported and got solved recently. An issue in rust-protobuf (segfault) when decoding specific values for which I sent a patch, and I think that's all. I also sent a patch to a very trivial bug in the fst crate.
To make it clear, it is rare for me to find bugs in Java's famous libraries (Guava, protobuf, etc.). That does not mean that rust compiler or rust crates have more bugs but simply that there is less users.
The productivity gain I got from using Rust instead of C++ largely (veeeerrrry largely) compensate for the time spent investigating bugs.