Awesome work Giles.  I kept meaning to get around to some of those
myself, after watching somebody type "mate" in their irb and making me
jealous.  Now I don't have to maintain a complicated .irbc across
machines, I can just install utility_belt.

I made a couple tweaks on my local copy, if you are interested.
Letting the editor commands accept a string has two really nice use-
cases: dumping the results of "_" when you get spammed by output, and
passing in a method_binding.to_ruby if you are using ruby2ruby (lets
you edit and thus redefine said method).  Both cases (_ and #to_ruby)
apply to pastie too:

http://www.timocracy.com/articles/2007/12/11/textmateing-a-string-from-irb-a-tweak-for-giles-new-gem-utility_belt
http://www.timocracy.com/articles/2007/12/11/utility_belt-tweak-2-passing-a-string-directly-to-pastie