Utu, believe just what you want to, I am using this the way it is advertised to work, Which does not work. Terrible is no exaggeration. I could also add "pathetic" for the ways the same types of errors keep on cropping up over and over again. And that the Debian standard kernel is at 3.2.0 - which in itself contributes to an own set of problems, not the least in networking.
Suffice to say that Klaus K has very good reasons for his policies with Knoppix. If you doubt, just give Debian-live a try, really using what are presented as the features.
Debian-live is designed for multiple overlays, but I doubt many use it. There are lots of bugs, and they are not benign.
The worst thing, is that you never know when and why things break. It has to do with all the promises that are not kept. For axample, you drop the overlay anywhere, the system just will find it. True? Not quite. I think I have experienced most of the possible combinations of errors during the last 24 hours. Overlay isn't mounted, it is mounted, but not used (that's a really terrible one), it is mounted and crashed, it is sandwich-mounted, it is not correctly updated, it is mounted, but not read correctly.

None of those problems were ever encoutered during 8 intensive years with Knoppix.