I spent a long time at universities hacking on Unix systems. I find the environment comfortable, and conducive to lots of computer sciencey kinds of things that I am interested in playing with. I think that the state of computer systems has been stagnant for a number of years, with no incentive to transfer research results or ideas in to practical systems. Part of the problem with doing this has been that it is very hard to transfer research code into "shipping" operating systems. The availability of Linux changes that. The source for everything is available. In order to change a system you have to have the source. A UNIX operating system and environment with full source is prerequisite to being able to fix and extend the system. Linux is starting to be the testing/proving ground for advanced development efforts, especially now that the basic UNIX functionality is approaching parity with commercial uniprocessor UNIXes.
The Linux distribution that I'm using is the Debian GNU/Linux system. The reason that I favor Debian is that the development process for the distribution is open, allowing anyone to become a developer and contribute to the distribution. Debian performs reasonably good bug-fixing and tracking. Debian's packaging and distribution system is at least as good as Redhat's RPM, although RPM's for projects in development are easier to get. I hope that this will change soon.