Open Source Software is precisely that: open. It is legal to modify it so you can change it to accommodate your special requirements. If you are not happy with your vendor, you can switch to another vendor that supports your software.
When you use Open Source Software, the work can be done cheaply and at the same time you are helping to generate local jobs.
When you don't use Open Source Software support or maintenance is provided only by an entity that has the right to exercise exclusive control over its sale or distribution.
The fact that open software is free does not mean it does not provide high quality. Linux, FreeBSD, Apache, PHP and MySQL are good examples of free applications which have earned tremendous credibility. More than 69% of all the web servers on the Internet run Apache and the most reliable servers on the Internet use FreeBSD and Linux as their operating system (Netcraft, accessed March 2011).