Thanks for your entry on Schedulator a while back. At work, we have been struggling with scheduling. I'd suggested making more use of bugzilla to track issues and tasks instead of just bugs. Then we had some management changes. Finally, we saw your entry. Looks like it was the tipping point. Your code is useless to us (for starters, we use Linux, Bugzilla, MediaWiki, and Python rather than Windows, FogBugz, GratefulTavi, and C#), but the documentation is wonderful.
We're looking at using bugzilla's existing time tracking features and adding better reporting. Your slip factor, automatic due dates, and load factors will feature in prominently, as well as Joel's original vs. current estimates. (Our existing schedules have had a certain "we've always been at war with Eurasia" feel, so there's no way to review historical slip factors.) We have a lot of other balls bouncing, but hopefully we'll be sending some patches back upstream eventually.