After witnessing companies being held back by customer lock-in by software organizations, I have become an Open Source advocate. We back that up by using almost exclusively Open Source software ourselves, and we would recommend the use of such software. It gives not only in many cases the cheaper option, but also allows for customization to levels not available on closed source software. In many cases it is also more likely to have longevity of usage, as the software is likely to be developed by foundations rather than companies.
This website was written, and is hosted, using Open Source software.