A bit lacking.. but....
I am using the heck out of this tool, but it does lack some certain features (like the ability to print). It gets rather hard to collaborate with people or to show managers what progress is and isn't being made when they are using Windows and I can't even generate html from this (files get saved as xml files).
I do notice however that the developers have some development going and are adding some more features, so perhaps by Q2 2003 this will be the definitive project management tool for Linux. :)
Tools like this do help, but if things like printing are missing from these kind of applications, there are many people that are forever dualbooting or vmware'ing a Windows installation in order to run MS Project or Office just to get things collaborated on in a sane manner.
An open, cross-platform journaling program.
A scientific plotting package.