I'm not really looking for a single correct answer. I'm just looking for some input regarding the inevitable "gotchas" Apple seems to sneak into every major OS X release that screw over a select handful of people before they have time to resolve whatever feature or app got removed in any given release. I want to know about anything at all; I'm a developer, so even lower-level system tweaks and restrictions have an effect on me.
Afaik. Xcode 5 no longer supports gcc or llvm 4.2
I still need to maintain some apps for 10.6 With xcode 4.x and 10.8 osx I could do this ok because I just symlinked a 10.6 sdk and could still use gcc or llvm 4.2
But upgrading to 10.9 I also upgrade to its xcode 5 so I could use the 10.9 sdk
I found even with the 10.6 sdk there is no ggc and llv 4.2. Clearly I did not pay attention to the press.
Luckily I still had a xcode 4.x app (using timemachine restore and keep both) that seems to run ok side by side with the xcode 5.