They are great as long as you do a few things:

1. When you change the strings, make sure you give them a good stretching as you bring them to tune, then pull on 'em a few more times and retune.
2. Spend the few bucks to purchase and install a Hipshot Tremsetter http://www.stewmac.com . This will take the place of one of your springs, and in the case of a broken string, the rest will stay in tune. I got about 20 of 'em and I love 'em.
3. Lock down the nut and give the strings a few dive bombs. Check your tuning, and retune. Usually after about 4-5 bombs, as long as you gave a good preliminary stretch, you should stay in tune.
Follow these few easy rules and you will stay in tune forever.

oops almost forgot, when you use the tremsetter in conjunction with a d-tuna, you can instantly go to drop-d tuning without having to retune. The tremsetter holds the floyd in place and the d-tuna drops the string... very cool indeed...

[Edited by hairbndrckr on 11-10-2003 at 02:31 PM]