This is a minor maintenance release. It fixes a few issues that showed up in Ubuntu 17.10 and Fedora 27, such as glibc switching to the openat system call which then had to be supported by rr's syscall buffering for good performance. info proc maps works in gdb during rr replay now. Of course various other bugs were fixed.
One interesting thing about this release is that it's the first to have guaranteed backward compatibility with an earlier release: traces made by rr 5.0.0 should be replayable in rr 5.1.0 (and any later release, I hope).