I am running on the Mac. On the mac, the menus show up at the top of the screen and there is another menu (titled Main after the class) - which is always there on all mac apps. It has an Exit option in it - in addition to YOUR exit option in the File menu.
If I quit with your option - it works fine and saves a user.prefs file.
If I quit with the Main>Quit option it must bypass that code and not save.
I think you will get all the performance benefits while compiling for 1.2.2 - you just don't get any new APIs - but there isn't anything amazingly trick until generics in 1.5. 1.3 was out for a really long time - so I would think you'd be safe moving to that (I am not 100% sure that the shutdown hook appeared in 1.3 so better check that)... but in the end it's totally up to you. I'm happy to have a workaround
