Had / running with reiserfs for quite a while now. It's great.
No problems so far.
You will have to rebuild your kernel with reiserfs inlined.
It's a bit hard to load the requisite module if the kernel doesn't know the filesystem type to read for obtaining the modules and root filesystem.
I got caught out by that problem and unfortunately forgot to have a backup arrangement.
Fortunately it was sorted out with some juggling.
You could be daring and run with devfs as well.
Again no problems and very easy with Debian :)

It looks like it's time to convert my old ext2 partition to ext3.
It gets a bit dull when the bleeding edge starts stabilising...:(
Reiserfs has been rather lacking in showstoppers for quite some time :(
Though I'm still having trouble running VMware on my 2.4 system. It worked before :(
If I can get it sorted out I might consider paying for registration.