How does data get "imported" into ML's new features? I'm a little concerned about upgrading to Mountain Lion right now because I'm not sure how some of the data I have on my machine will get shoehorned into Mountain Lion's new apps and features.


Does "Notes" start out clean? Does it import your To-Dos from Mail (the way Notes would sync before iOS 6/ML)? Or does it import notes from Stickies?
What happens to all of my Reminders in iCal? Do they automatically get imported into the Reminders app? Will I end up with duplicate Reminders resultant from iCloud issues?
I have the iChat setting turned on that saves all your chat logs. Will I still be able to open them in Messages? Will my iMessage conversations start to get saved in the same logs? (Is chat logging even still in the Messages app?)
I know Gatekeeper is enabled automatically, so what happens to always-running processes that I have set to start when my Mac turns on? I don't know if apps like Dropbox, LogMeIn, f.lux, or any of the others that start up as soon as I boot my machine, are signed with an Apple Developer ID, so will this cause big issues when I update and all of these unsigned apps try to run at once? (I plan to disable Gatekeeper minutes after upgrading, but I don't want it to cause issues that might keep my machine from booting up at all.)
Notes will import from the Notes folder in Mail. They no longer appear in Mail, but are still an IMAP folder.
Reminders will import from the task calendars in iCal. They no longer appear in Calendar, but are still ical files.
Messages pretty much is iChat, with a different UI and an extra protocol (i.e., iMessage, which is really just XMPP). You can still save logs. You can still read your iChat logs. If you have iChat set to load old conversations when a window opens, the iChat conversations will appear in Messages when you open it the first time.
For Gatekeeper, most apps are signed already so you won't have to worry about it.