Sidux deserves nothing but praise in my opinion. Here's a debian-based live cd that has managed to stick to their schedule for their first three releases, has a team of developers who listen to suggestions on their forum and irc, and encourage and accept contributions. They also have a supported installer, which reportedly leaves you with a plain sid install, hence avoiding the complications inherent to the repositories mix on which knoppix is based (but obviously leaves you with the occasional breakage debian unstable is subject to - beginners beware). Being current also means they include a post-1.0 version of ntfs-3g, which is very solid - writing safely to ntfs is finally possible.

Keeping up with linux/debian is daunting for anyone, and Klaus has done it essentially on his own for very long... Whether he is still interested in maintaining his creation or not, we remain forever indebted, and so are the developers of the many live CDs that ran with his ideas. Sidux is definitely amongst the best debian-based ones.