I am working on a bunch of utilities in ruby to process logs and parse hundreds of webalizer reports. I track my work with monotone which runs fine on Windows. I also use monotone to track appliances configurations.
One on my scripts analyses about one thousand of HTTP documents of ~50KiB each. ruby net/http module is perfect to retrieve them. This script is quite slow because of the regex it uses like %r|Foo.+?<B>(\d+)</B>(?:.+?Bar.+?<B>(\d+)</B>)*|m. But as the script runs every night on my desktop, I don't really care if it takes 10 seconds or 10 minutes. It is clean and easy to extend and that's what matters to me.
I have found that slow regexp is a common ruby issue : here's a simple demonstration. More details about regular expressions performance.