Some time ago, I decided to learn the ruby programming language. This was on the advice of a friend. There was a rough choice between ruby and python as two fairly popular, up-and-coming, dynamically typed scripting languages in wide deployment.
After that, ruby on rails came out, ruby popularity exploded, and it looked like I'd made the right choice.
Since then I've made the decision to stick to learning python and abandon ruby. This page attempts to track why.
rexml - core library!
essentially unmaintained, accepts invalid XML, written with a loop of regexps (urgh)
http://www.tbray.org/ongoing/When/200x/2008/06/10/RX-Work - Tim Bray attempts to write a sane, pure ruby XML parser, finds it hard due to performance issues with integers.
http://innig.net/software/ruby/closures-in-ruby.rb - 7 different ways of representing closures (2-3 of which are not really closures)