I have just started working on a poor man's install of Debian 8.0.0 live - The 7.6.0 version has been my daily OS for the last 6 months, only occasionally using Knoppix.
I have used it almost exactly the same way I use poor man's installs of Knoppix, the main difference being pure 64 bits. And with that, somewhat better performance, easier handling of huge amounts of data, Oracle XE 11g, and - in fact easier remastering (mostly a Debian effect).

I had almost forgotten how much the system is in need for a healthy amount of Knoppification, but I run into the problems now, on upgrading. That is in itself an important reason for creating a derivative. Another reason may turn out to be the conversion to systemd init in Debian 8.0.0. I don't really have strong opinions on systemd (I think Linus Torvalds' comments are to the point), but there are definitely things that should be adjusted (not only the use of binary (!!!) log files). I'm curious about the new init process, initrd.img has grown massively, from ca 13 to ca 35 MB, and the system may have distanced itself even more from what I think is Klaus K's very efficient and rational approach to system init. Klaus K's minirt.gz is 950KB, in comparison.

Decisions about and development of systemd will also affect Knoppix users, as Debian packages are now allowed to be dependent on systemd.
I think engagement from Knoppix users would be beneficial for all - even themselves