I'm a huge fan of regular expressions; they're the swiss army knife of web-era development tools. I'm always finding new places to use them in my code. Although other developers I work with may be uncomfortable with regular expressions at first, I eventually convert them to the regex religion sooner or later. If you're working with strings in any capacity at all-- and what developer isn't-- it's hard to deny the flexibility of regular expressions. Why use 6 lines of procedural If..Then blocks to process a string when you can do the same thing in a concise, 20 character regex pattern? And if you put that same pattern in a .config file, you can now change the behavior of your app without recompiling. It's less code doing more work.
This is a companion discussion topic for the original blog entry at: http://www.codinghorror.com/blog/2005/02/regex-use-vs-regex-abuse.html