- Initial cost. I don’t have to worry about tons of licensing options and cost upfront. I know that if I use GPL software, even if I spend software costs, I don’t get ripped of when more licenses are needed. Most GPL software comes with reasonable cost too.

- Total cost of ownership. For most of the general purpose work (any thing other than super speciality application), this is almost a no brainer. You don’t spend money again and again to upgrade your licenses, you get patches rigorously on time etc.

- Trust worthiness of software. Unlike closed source, open source software has more chance of getting exposed to people with no financial interests. This really improves the trust worthiness - you don’t have to worry about claims like "oh, we want to get information from your computer to our server, to serve you better and to better analyze your problems". If need help, I’ll call the vendor rather than vendors collecting information on their own.

- Reliability of software. Well known open source software like JOOMLA, MAGENTO, Apache, Linux, Free/Open/NetBSD, Samba, Zope etc are worked on by people who do that work simply because they are proud about it. That, IMO, is the best ownership. You get code with lot of heart behind it. For most closed source software, that feeling of responsibility that any one and every one can see the code and hence you might be held responsible simple won’t be there. Just how would you like if your constitution is a closed book and the judges alone can look at it and decide whether you broke the law or not?

- Support. This is often brought up often by anti-open source advocates. I think, in reality, open source offers the best support, if you’ve competent people in your team. Either you can get help from the community or you still have the option to go through the source and fix it.