When you tell the average computer user that Open Source software gives them access to the source code, they will tell you "I don't want access to the source code." This is not an effective selling point for many users (especially home users, small business, or any other group that doesn't plan to customize their software).
But there are practical benefits to free / open source software (FOSS) applications, even if one never touches the source code. They are just not always evident without some thought. This is why a list might be helpful.
Practical Benefits of Free and Open Source Software
Please add to this list! It is in approximate order of wow-itude.
no spyware or advertising spyware and advertising can't live in open source software (the feature would get removed and the author would quickly lose respect)
great applications don't forget, it's not just windows vs linux/gnome -- users get an office suite, graphics viewers and editors, archive managers, etc. with the package
$0 you don't have to pay for software (although it's confusing to some people why Linux often does cost money). But companies _may_ charge for delivery, installation, support, and custom development.
no abandonware applications don't get abandoned just because the original author gets bored, or when the company goes out of business / changes focus. if it's popular software, it will most likely continue to be maintained by someone.
open file formats when source code is open, file formats are open, too. open file formats tend to be supported for much longer than closed ones, so data doesn't get "stuck" in proprietary formats and lost. (examples would be nice here, I'm sure there are plenty)
free market development in the rare case that an application's authors are not cooperative, there is always the option of hiring a contractor to fix a bug, add a feature, or otherwise customize the software for you (with proprietary software, if the vendor doesn't listen to you, you're out of options)
sharing you can share it with friends legally
free market support because everyone can look at the source code, anyone can provide support for the software, thus creativing a free market for paid support (with proprietary software, the support usually comes only from the person / company that produces the software, or a subcontractor of their choosing)
transparent development process the majority of FOSS projects make the list of outstanding issues available online, as well as outlining future plans. anyone can become involved in product design. if you can make the case for a feature, it will likely be accepted.
no need to keep track of licenses this is a big time waster for medium to big companies, and is potentially quite dangerous if they screw it up
no need to wait for a single company to fix bugs if a bug appears and you need it fixed quickly, you can do that on your own or pay a third-party to do it. (you do not need to wait until a single supplier fixes a bug for you.)
We need some statistics for these:
faster development time?
more eyeballs = fewer bugs?
bugs tend to be fixed faster?
useful links: http://yoderdev.com/oss-future.html