I'm a great user and adept of free software, but I must confess that I'm more attracted to the "free beer" side of things rather than the "free speech".
But for some reason each time I change a bit of open source code and make things work just like I want them to, it gives me an enormous satisfaction! There's 3 episodes that I really enjoyed on my open source adventures:
1. I patched the linux kernel! It was just a small patch to make my CD-Rom drive work, but it was tremendously rewarding to see the little light blink on that drive! (I didn't publish this one because it was a really old cartridge 1x CD-Rom drive)
2. I patched Kannel. This was amazing because I did the patch at the same time someone asked for it on the mailing list. So I send it to the mailing list and it is now part of the Kannel code!
3. I've been trying out Total Commander on Windows. It's a really good file manager and has an iPod Plugin. Turns out the plugin doesn't work with newer iPods. But since the source is available at the author's site, I downloaded it and fixed the problem! (I'm now talking with the author to get the patch published)
The funny thing is I believe I would've done the same even if the software wasn't free as in "free beer". Actually I would be thrilled to be able to fix some bugs and annoyances in some paid applications. Unfortunately I don't have access to the source code, so I'll just have to live with them...