I’ve been using Linux/UNIX for about 20 years. I am also Assistant Director of the Boston Linux and UNIX Group, and have contributed to several open source products. In general, I find open source software more flexible, more transparent (no security through obscurity), and more focused on what’s needed instead of what marketing says would be cool. I like that open source software is usually developed modularly, with separate components each doing what they do well, each designed to be combined with other component, each with its inputs and outputs documented for fitting Tab A into Slot B. Open source’s community support model (with a sufficiently large community) is often far superior to calling tech support. All that said, I still believe very strongly in “the right tool for the job”. Sometimes open source is not the answer.
Just like commercial software, it’s important to evaluate not only how well the software suits your need, but the “health” of the product and its creators. Just because it’s still available doesn’t mean it’s still supported, updated, and in common use. That may not be a deal-breaker for you, but it does need to be factored in to the decision.