I love Debian distributions, including the original Debian Stable, Testing, and Unstable (Sid) distributions. I have at least two Debian Lenny instances on my computers. But I really love Debian derived distributions, sometimes even more than Debian itself. Three of them that really stand out for me fit neatly into three niches and with these three distributions I could (if I did not love testing distros so much) do all of my computing with them.
1. I love sidux because it gives me a fast, cutting edge Debian Sid based system that works really well, and in two years of use, has yet to fail me. I can actually use it as an every day system and it comes through with great performance and features.
2. I love SimplyMEPIS because it really is simple. It is also stable, clean, and reasonably fast. Warren Woodford, the SimplyMEPIS founder, does such a good job with his software that even his test releases are superior to many other released distributions.
3. AntiX, based on SimplyMEPIS, is nearly as solid and stable as SimplyMEPIS, but it uses Debian Testing by default (which you can change to Stable or Sid). It is fast and lean, but it is also flexible. It is a curious and awesome blend of SimplyMEPIS and sidux - it has tools from both of them, so you can imagine, since I like each of them so well, that I am also extremely fond of antiX!