Hmm, I think I should definitely jump into this thread somewhere....
I first tried Linux shortly after the first public announcement (version 0.12). I played with it off-and-on over the years, but didn't make the jump to being a full-time Linux user until '96 or '97. I had tried various distros (SLS, Ygdrassil, Slack, Red Hat), but the one that really won me over was Debian. By the end of '98, I'd joined the Debian project, and was a contributing, voting member till just a couple of years ago.
The main thing I liked about Debian was that it allowed you fairly fine-grained control if you wanted it, but provided reasonable defaults if you didn't. The other two biggies at the time were Slackware, which forced you to micromanage the whole system, and Red Hat, which basically forced you to roll your own if you didn't like the defaults. Debian was (and to a lesser extent, still is) a more complex system than either of those two, but it was so well-designed that you'd barely notice unless you went digging beneath the surface.
The other thing I've always loved about Debian is the ease of upgrading. Ubuntu users talk about how nice and "clean" a new install feels; Debian users brag about how long it's been since their last full install (2002 for me). Which is sort of peculiar, since Ubuntu is basically Debian-simplified-for-the-masses, but then Ubuntu has its fixed release schedule, which takes priority over smooth upgrades, while Debian follows a release-when-it's-ready approach.
Anyway, I'll keep an eye on this thread. I'm sure I have tips and tricks that some folks will find useful.