I've been using open source software on and off for quite a while, and it constantly amazes me how much there is out there and how well supported it is. That the huge package repositories of Debian and Gentoo actually get tested and sometimes maintain their own patch sets of different software packages seems like an incredible amount of work, and it's volunteer supported.
There are recurring complaints about open source, but in some ways its a measure of what people come to expect from it. Say 10 years ago, you had to muck around with a lot of stuff and eventually it worked and that was good enough, some of the good projects had a small dedicated group and you could get pretty good help from the forum or mailing list. These days it almost seems like every large project has an army of people doing everything from testing, to documenting and programming.
A major complaint used to be about the huge number of window managers available. A lot of the complaints were saying that there wasn't enough standardization, that these other projects were diluting the effort. But then GNOME and KDE got more mature, and those complaints died down. It seems like the number of window managers wasn't the real problem, just the lack of some nice defaults.
This is great, because I happen to really like this whole scene of experimentation that goes on because you can change the window manager, rip stuff out, add stuff in, and have different ways of organizing how you work with your computer. The other thing that is nice about this is that the X.org people think about how to introduce new features in a window manager friendly way. This slows development down, but just looking at the new things that are coming in to X.org such as indirect rendering, new architectures for drivers and MPX makes me think that there's only more good stuff to come.
There's a lot of back-end work going on that doesn't look too impressive, especially when your other software stops working for random reasons, but from a programmer's viewpoint, it looks clean and thoughtfully designed. I can't wait to see what's going to be built on top of it.