Works really well once you've sorted a few quirks - it's what finally allowed me to fully switch from NetBeans to Vim about a month ago.

Hint: add the following to your .vimrc if using MacVim:

    let g:ruby_debugger_progname = 'mvim'

Running specific tests is also a snap; just place your cursor in the desired spec and command-shift-r (built in support for spork).

I'm not in any affiliated with JetBrains (swear); just a satisfied customer.

But I always thought that RadRails was pretty good. YMMV

http://aptana.com/products/radrails

I find it useful to be able to see the current stack, drill into variables, view my code with syntax highlighting, and the current line all at the same time. It helps me understand where I am.

(I won a free license as a prize at a conference a few years back and it's really quite nice.)

The rewrite of ruby-debug for Rubinius currently supports syntax highlighting via CodeRay. See https://github.com/rocky/rbx-trepanning or https://github.com/rocky/rbx-trepanning/wiki/Terminal-Colors for how to set that up.

The github project Emacs interface for the newer series of debuggers is https://github.com/rocky/emacs-dbgr.

But as someone else pointed out, it sounds like you'd be happier using an IDE such as one from JetBrains, Aptana, or Eclipse.

It would make things so much easier for me.