I just opened a utility from late last year and went to build it with today's tip. I got quite a few errors, all in chunks of code that were for 'pre 10.5' stuff (ex. delegate is now a private member, so DoPlatformSpecificInitialisation() can't do pre-10.5 thread magic).
Simply bumping the SDK from 10.4 to 10.5 in Introjucer took care of the problem (and is fine for me, 10.5 is OK for a minimum support level). If you want to drop pre 10.5, fine by me, but you might want to take the option out of Introjucer.