Did you try using rust-gdb or rust-lldb? They're wrappers for gdb and lldb respectively that make working with Rust code a lot nicer. They ship with the Rust compiler.
Yes. I couldn't single step through a simple program without delving into assembly code. Couldn't list the program. Breakpoints weren't working. I think part of the problem was working on OSX. I was reading some Rust issue related to the debug info generation. Although the issue was closed I think it's still a problem. Oh well.