I haven't tried with FF personally, but the issue I have is that the traces are huge and reverse execution through memory-intensive codepaths takes a very long time, making the experience really slow. Or you can run a release build (with optimizations), in which case everything gets inlined, your asserts get nuked, and you're unable to inspect state well enough to figure out what's going on. In most cases, an ordinary debugger provides a better UX for me, but for the odd memory bug untraceable by normal hardware breakpoints in a traditional forward debugger, it comes in handy.