It's probably easier to do if you have a spare hard drive. I feel much safer doing it this way than using an all-or-nothing approach. I'm not saying that convertfs doesn't work or even that it's buggy -- just that I feel more comfortable copying the data to a new drive, booting from that, letting it run a few days to see how things are working out, then retiring the old drive.
I used the following guide (
http://www.losurs.org/docs/LDP/HOWTO...ade/index.html) to do my filesystem change, with slight variations (I partitioned the new drive a bit differently than the old one). I can provide the details, if desired.
I've now been running ReiserFS for several days without problems. It does seem a bit quicker than ext3.
Garry