Linux in the US Federal Government?

Grech asks: "I work for a US federal agency that replaces its workstations and attendant software every 3-5 years. At the moment, the environment for most workers consists of an OS, an office suite, a UTS60 emulator, and an X Server. Logic seems to say that when all this gets ripped out and replaced in a year or so, it could be done cheaper with Linux, but a case will have to be made, and a strong one. I've got the arguments, but I need the numbers and the anecdotes to back up such a huge project."