In the company that I'm working in, TestNg is being used, and we can't commit anything unless there is a test  case for that one, and before deploying all the test cases are ran, so they're sure that nothing's broken, and also we use Emma to get the rest coverage report.
and I have found it really useful to write test cases and i believe that's why their applications are really working!!
but we have just one difficulty with test data, we are not sure how to generate the data, right now I'm using Xstream to generate some xml files based on entities and some parsers to read the data from these xml files and persist them to data base, but this is a really controversial issue here and we're still discussing it more than two months, I was wondering if you have any idea about how to generate the data?