Kayako (Score 1)

We're using kayako (http://www.kayako.com/) as our user facing trouble ticketing system. It's not free (cost us something like a couple of hundred US$) but it is very functional and includes mechanisms to track costs. It has a bunch of stuff included that we don't use - like live support etc - as well as a bunch of cool stuff that I haven't seen elsewhere (like AJAX based searching of knowledge base articles as someone updates a trouble ticket). It also integrates nicely with our LDAP based single signon system. We support 6 remote offices and about 200 users with the product. You can even pay an extra license fee to have a non-branded version.