Inviting the public inside a product's development builds community and trust. It also sets the platform for increased reliability. Fans of open source programs are adamant about reliable software and highly criticize commercialized versions for being buggy and error-prone. Avid fans even proclaim commercialism is the cause of shoddy software.
Another benefit that open source brings to light is the speed at which its products are developed, enhanced, supported and distributed. This is because the people who regularly contribute to an open source product do so for unmotivated reasons (other than perhaps to feed the ego.) They're highly talented, they're available, and they care. Bringing money into any project can almost mean instant death. It can kill motivation, desire, and a true willingness to create a good product. In a commercial setting, participants work for a paycheck rather than for the product. And this is what puts open source projects far ahead of its monetized competition.
As a software user, this means you can contribute to an open source project as well, and help to develop it into a product that reflects your direct preferences. You aren't "stuck" using open source software the way you would be stuck using an expensive word processor or database. You have the same access to open source software as its programmers have and in essence, you are your own customer!
Perhaps at this point you're wondering where you can get in on this wonderful opportunity. There are plenty of open source opportunities sprinkled across the Internet and they can be easily found though any search engine. Google "open source project" and you'll be sure to find more resources than you can shake a stick at!