Quote:
oh, haven't seen kidde's "dd", too...
I think dd is the better choice

Yep, using dd from what I've see is a much better choice. I've seen that used numerous times for backing up raw data off a disk, but I've never seen cat used (although I may not be looking in the right places).
I think using either dd or even tar would work will. I've had most experience with using tar, but then again you would have to mount each filesystem and the backup would be file-based rather than raw data-based (as dd is). I don't know how you feel about commercial products (and I'm not sure if ReiserFS is supported with this), but I've been messing with Acronis lately and it seems to be a good choice for doing a full-disk backup if you don't mind spending the money. A trial version is available if you would like to test it out:
http://www.acronis.com/
Now I'm not familiar with FSF and SFS, and neither may Acronis. dd really may be your best bet:
http://www.inference.phy.cam.ac.uk/saw2 ... tions.html
No matter what you use, I would highly recommend not trying to perform the backup with any of the filesystems being used. In other words, boot from some type of boot CD. Sometimes you can get away with that, but if you want to make sure that every file in your backup is good then make sure to use another boot device.