A few days ago I gave QT Parted a try (from a Knoppix 3.6 disk): I shrinked my NTFS partition to leave more room for other OSes (not that space is a problem here, but I wanted to try it). The program is awesome: very easy to use (looks a lot like Partition Magic) and it did the job quickly and correctly.
However, yesterday's evening I tried the same but with a ReiserFS partition. In few minutes, the partition was shrinked to half of its original size. Afterwards I tried to mount it, still from within Knoppix. Everything seemed to be OK.
But it was not so nice as I expected. I rebooted into my Debian system... and fsck.reiserfs was started. Lots of errors flooded the screen, just to tell me a bit later to fix the errors manually.
Got to the console (which still worked), tried another fsck and got the same errors. Now I noticed a suggestion that told me to try the --rebuild-tree flag. Oh, it may fix it... so I tried. The process seemed to go fine, but things got only worse. After a reboot, nothing worked; even GNU GRUB failed to read its stage2 correctly.
So I gave up. I had nothing important in the partition aside apt's cache (not a problem since I've already downloaded everything again). From now on I'll continue to keep my Linux installations under Ext2 (or maybe Ext3), mainly because they can be read (and written!) without problems from NetBSD. And they can be safely resized (I can always go back to Partition Magic 5), in case I want to try another OS.