Consider this a sister thread to my Wikipedia one.
I like open source software and use it every day. Linux, of course, is a prime example. The mind map software Freeplane is another. And there are a number of tools I use at work, every day, that are open source, written by people who normally get paid to develop ridiculously expensive products for Fortune 500 companies. They are updated often by their creators, but also regularly patched by others who use them. Bugs are fixed very, very quickly, in most cases, and features are added if people want them and somebody has the time and know-how.
A case in point. I was presenting at a conference a year or two ago, showing stuff that I had developed, using a piece of open source software called Calabash. The author, Norm Walsh, was sitting in the auditorium, listening to my talk.
The W3C standard Calabash is based on, XProc, has some built-in problems. There are features it sorely needs that just aren't there yet. And one of these missing features had forced me to do a rather complicated workaround, which I was explaining to my audience, among them Norm, the author of Calabash.
I finished my talk to reasonably enthusiastic applause and sat down to listen to a colleague's talk, hooking up my laptop and checking my mail while listening.
One was from Norm. While listening to my talk, he had designed an extension to Calabash that fixed the very problem I had outlined to the audience, literally minutes before. He explained his basic idea and asked if that would fix my problem. It did.
More recently, I based my Prague talk on several open source technologies and worked with their authors to develop these technologies so they'd do what I needed them to.
My demo, of course, is now also open source, thanks to my boss who graciously agreed to release it as such.
Compare this kind of rapid development with proprietary software. I could pick a large one , like MS Word, but a better example is actually Microsoft's Solitaire Windows game.
It's been around since the 90s, at least, and certainly before Windows 95. It's not that complicated but there are bugs in it that have been around since I first used it on a Windows 3.1 computer. There are missing features and there is some built-in ugliness, and yet none of it will be fixed because it's proprietary and MS won't set aside the budget to do it.
There are some brilliant open source alternatives to it, though.