Am I correct in understanding that the slackware-current/testing/ package kernel-generic-2.6.8.1-i486-1.tgz does not support Reiserfs 3?
I am running 2.4.x and all my drives are v3, so I don't see how to try the kernel.

I looked at the included .config file....it appears that Reiser3 is only a module with that kernel. So, if your root is Reiser3, it won't work, no.

When 2.6.7 was in testing, it came with the read-me file which teach us how to make the initrd to support reiserfs and ext3 an etc filesystem.
ftp://ftp.slackware.at/slackware-10..../README.initrd

Quite easy and straight forward.

Pardon, if this post doesn't exactly have to do with the problem, it is more of a question about ReiserFS in general, and I didn't want to start another thread. I have heard from some people who has used ReiserFS, and that although it's performace is great when it comes to journaling the partition, it is however noticeably very slow, compared to ext2 and 3 , and even though ext3 is also a journalizing FS, and XFS too, I was wondering, if there had been any changes to ReiserFS to make it's performance more efficient, and between ext3 , XFS and ReiserFS , which one would be the best to choose for not just performance wise, but for journaling....

My experience and many others is that ReiserFS3 is much faster than ext3.
XFS and JFS can be faster in certain circumstances like large sparse databases but for general use reiser is the best journalling file system

ext2 should be faster, it's not journalling at all.