Apple professionals use Xcode. Using different tools than the ones Apple uses leads to a lot of problems that Apple are not interested in fixing.
The days when a company like Metrowerks or Symantec could be a viable third party IDE supplier are long gone.
I don't do Apple development as much anymore, but I used to write in AppCode a lot and used Xcode only to build.
Alongside Xcode I find BBEdit very useful for editing data files, diagnosing merge problems, writing shell scripts, etc. I still do almost all my real coding in Xcode to use the autocomplete.
Tower is useful for anything non-trivial in Git. For basic operations the Xcode Git support is useful.
AppCode uses xcodebuild etc under the hood and xcodeprojects to configure the ide. You aren't going to get any bugs in the compilation etc process than you would in Xcode.
I believe AppCode uses XCode behind the scenes for most of the magic stuff anyway. It's just a more capable facade.
Note: I'm not connected in any way to Jetbrains, and I have not used AppCode myself, but I used other tools from them, and they're quite competent, I'd say.
[0]: https://www.jetbrains.com/objc/