We're still working on the refactoring and have not gotten to adding new functionality yet. However, our client has just discovered that this will, in fact, cost money
We're using chromatic's Test::MockObject for the unit testing. It's a great module that allows unit tests to isolate the current unit's functionality, but integration testing will likely uncover many more bugs. Already, we've found some weaknesses in our current approach and are rapidly working to deal with them.
On a personal note, I just picked up a 700 megahertz Pentium III with a 15 gig hard drive and a 17 inch monitor for only $135US. Now I have my first Linux box at home. Hooray!