The problem with closed-source software is that sometimes a feature is not really a feature. Take, for example, Apple’s incorporation of HDCP into their new notebooks. Basically, HDCP is a technology designed so that everything between the content and your eyes (graphics card, cables, connection types, display) has to support HDCP and be designed to prevent leaks that could allow someone to pirate the content. Sounds like a great idea, right? No.
The effect of HDCP is, in reality, nothing more than bothering legitimate users and potentially forcing them to either pirate their content or buy new equipment. I could rant on forever about how DRM is a hopeless arms race that appears to have little effect except to lower the value of DRM-ed content and annoy users, but that is not the point I am trying to make. The point is this: HDCP is not exactly a feature that you would want in your computer. With proprietary software, though, you are stuck. You can complain, but you are at the mercy of the vendor.
If you run open-source software, on the other hand, chances are someone will have a version out without whatever anoying feature was introduced within a day. More generally, this means that even if you never want to see or touch a piece of code, there are still advantages, since others can. Really, it is just like opening up a phone to third-party developers. You will probably never write an application, but you will still benefit.