Unfortunately I am not on my main system so can’t confirm this myself, however multiple readers have reported losing presets in 3rd party plug-ins for Aperture, along with the plug-in registration. Registration is of course easy enough to rectify — just re-enter your serial number — but lost presets are something else entirely.
If you haven’t yet made the upgrade to 3.4, and you’re using any plug-ins (such as Nik Software plugins), and you’ve made any custom presets of your own, be sure to export those before proceeding so you can re-import them after the upgrade in the event they are lost.
I’d like to think that these presets are files or preferences stored somewhere in the system that can be easily recovered from through one of your many backup methods (you are backing up regularly, right?) but I can’t verify this myself right now.
Thanks to reader Patrick Curry, we have a recovery solution. Check the tip here.