These variables can be used to tracking specific bits of information that GA wouldn't call out on its own, such as how many people click a live help link on a site(mentioned in that post). Seeing a spike in that stat might suggest a problem with your design making it difficult to find some piece of information, for example. One site I've done work on has a pay wall and multiple subscription levels. By creating a variable for each level, it's possible to then check activity for them as a group in addition to everyone all together.
Whether and how useful the variables are is necessarily dependent upon what you want to know and then setting up a variable for it. If you're not using Silverlight on your site, then you probably don't care about that "no silverlight" var. You also might want to ask whoever added it why it's there. Note that something might be doing it automatically; for example, Yoast's Google Analytics plugin for WordPress has an option that will add a bunch of these.