Small update:
I'm now finished with the first round of Knoppix package selection installation on a Debian 6.0.1-64 system with LXDE/Openbox. The majority of packages could be found in repositories, but there will probably be quite a bit of compiling necessary here, too. Knoppix and std Debian differed more in the package selection than I would have expected. And I already miss the simple backup with Knoppix!

It may be a coincidence, but I have had quite a bit of hardware-related trouble with std Debian - on a machine that runs Knoppix without a glitch.
And things run a bit faster on 64-bits, though differences depend very much on tasks. I have noticed between 0 and 30% speedup so far.