After getting frustrated with ruby debug on 1.9.3, I realized that pry-nav and pry-stack-explorer are an excellent replacement for ruby-debug. After using pry for a while, I doubt I will return to using irb and ruby-debug.
As the author of pry-nav, I'm really glad to see more people using it! Thanks and please file issues if you get any odd behavior. I've been trying to improve the tracing.
Perhaps I'm wrong, but I don't think Pry can do "step" and such? I've been using Pry as well but I'm still very happy to see familiar ruby-debug back!