We have started to use trac as a base for development on almost all internal projects now. And the more i use it the more i love it.
Right now ive started building a hosted trac service. So that my company can provide trac to projects and other companies.
Templating and mass hosting isnt that hard if you have a dedicated machine for svn and trac. With a quite and simple configuration many customers can reside on the same machine without seeing each other.
(I will try to write a tad more on trac .. next will be building themes for it and install some plugins to secure it for company use :)