I have used Library Manager for several years now. I have found it to be very stable and have encountered no problems.
I did pay the upgrade fee but felt it justified because the program is well supported, does what it claims it will do, and has been a real life saver for me - my PB hard drive could not possibly fit all my iTunes cuts! But I do keep a good number on my powerbook - duplicates from my master collection - so I always can play iTunes.
The transfer files to another iTunes folder does not work smoothly, but that is my only hesitation. Everything else works great, especially the save feature.
I am very glad to have a good program that enables me to do this.