I downloaded and ran MrClean yesterday which resulted in a wipe of my iPhoto folder. I'm running OSX 10.4.6 on G5 Dual 2.0 mhz with no other problems. Launched MrClean on my pictures folder. As noted before, no "progress bar" movement but spinning wheel suggested it was doing something. 6 hours or so later I return to find the program has crashed completely. At first glance, no files appear missing and then I launch iPhoto and discover my iPhoto Library is gone. (iPhoto from iLife '08) Having worked for two days with the new iPhoto and events and such, I lost a lot of work since my last backup, thankfully only a few days.

I would call this version "unstable", with a poor user interface. If you simply must try it, then do so only after making a complete full backup of your iPhoto files (as a minimum). This is good practice anyway, but I thought you could use a horror story to remind you how important it is.