I just downloaded Mozilla's Firefox 3.0 Beta 4, and loved what I saw:
See that? Firefox is localized into a wide range of languages, which is great. But what I appreciate even more is that it treats Windows, Mac OS X, and Linux as peers. In Microsoft's world, software runs solely or best on Microsoft's operating system, database, etc. Given the chance, most proprietary software companies behave like this.
Not Mozilla. Not Eclipse. Not Zimbra. Etc.
There's something about open source that speaks up for the potential user who isn't part of the mainstream. Somebody, somewhere, is like that person and has contributed the code to bring the outsider in.
No, not all open source is written for every platform in every language. True open source, however, doesn't mitigate against someone doing this, which for the more popular projects generally leads to a myriad of "itches" getting scratched.
I love Firefox. I love that it doesn't treat me like a second-class citizen because I use a Mac. I love its egalitarian (and now super-speedy) nature.
This is how software should be written.