Thanks Werner (and Klaus ) for your prompt reply.

It's been almost a month since this new v7.2, and I will now report on my user/noob experience with apt, video and sound issues about my fresh install of Knoppix V7.2 DVD on my HD (Samsung SSD 840 256Gb - AMD PhenomII quad core - 6Gb ram).

Apt wise, I don't have any issues anymore. However, I have learned at my expense that, if I don't want trouble with broken packages, I better use Preferences-->"Software Settings" (i.e. gpk-prefs), rather than synaptic (i.e. sudo synaptic-pkexec), to check for upgrades/updates. So I would recommend the option "check now" of gpk-prefs, rather than the option "Mark all upgrades" of synaptic.

Video wise, I have a ATI Turks Radeon HD 6570, which is connected to one Philips monitor via DVI (main monitor and desktop) and to one Samsung TV via HDMI (secondary monitor, which I want as desktop extension). I managed to make it work like I wanted, with "Preferences"-->"KDE system settings" (systemsettings -caption "%c" %i) -->"Hardware"-"Display and Monitor" etc....
In the previous Knoppix version V7.05 however, this was easier to achieve via the utility "arandr", which now sadly does not work anymore. Moreover, the configuration I have managed with the "KDE system settings" does not hold between boots, i.e., when I restart my PC, I have to go through the systems settings configuration again in order to extended my desktop on the TV. How do I make my changes persistent? Why does "ARandR" not work anymore?

Audio wise, I also managed to make it work as I wanted, but that was much more difficult.
Technically, the ATI Turks Radeon HD 6570 video card is also an audio device, which sound output I would like to use onto my TV, but could never make it work under K (or any other Linux I have tried so far). I know that the hardware and connection is OK because it works on M$ W7. For now, it doesn't matter too much, because I have analog sound through my monitor, and also digital sound through optical S/PDIF (see other issues below) hooked to the optical port of an old 5.1 power amplifier. In the future, I might upgrade to a more modern home cinema amplifier, so I will have to use that sound through the HDMI port. I hope by then I will have managed to make my ATI-HDMI binding work properly or easily, otherwise my wife will force me to go back to Win$ for watching movies with digital sound. I know Klaus has worked hard on those HDMI issues, but unfortunately for me this is still a no go.

S/PDIF issues:
That's what worked for me using the optical audio output, but via the on-board audio device (do not the ATI HDMI).
I created a file /etc/asound.conf following this thread on alsa: http://johannes-bauer.com/linux/dolby/?menuid=3.
Then, using this (french) documentation as guideline :
http://passion-xbmc.org/tutoriels-li...c-sous-ubuntu/
I decided to copy the file from the latest Ubuntu Raring 13.04 distribution because that worked OK: /etc/modprobe.d/alsa-base.conf.
I just added this line at the bottom (barely knowing what I was doing though....):
"options snd-hda-ati model=6stack-dig"
However then, the only action that caused my S/PDIF to work was to tweak into [alsamixer], but then again, my changes do not survive PC reboots. Again, how do I make my changes persistent here also?

If I want to evangelize my wife into Linux (and particularly Knoppix), I can certainly not ask her to go into all these tweaks after a PC boot to have a full-fledged working OS! Right now, Knoppix/Linux is much faster and nice-looking than the other O$, but things are not quite so easy under the hood for noobs like me