The Arduino IDE is great and provides plug-and-play and instant gratification but, sometimes, complex sketches require a more powerful IDE.
Also, some niceties are welcomed, as syntax colouring, line numbering, function highlighting, code-sense, template with parameters for a function, check-as-you-type, click-to-error, tool-tip texts, object browser, self documentation, git repository management, code snippets, bookmarks, ...
embedXcode supports Arduino 0023, 1.0x and 1.5x repositories.
• New! Release 51 includes full automatic project configuration: .pde or .ino sketch are declared as C++ code; all the cores, variants and libraries from the installed platforms and user's libraries from the sketchbook are added as resources for code-sense!
I tried Xcode because I own a MacBook. Xcode is flexible enough to deliver code-sense with just being provided the paths of the source libraries.
And the main benefit is faster development.
The paradigm is that a sketch consists on a standard C++ code, and thus processed accordingly.
embedXcode relies on a modular set of makefiles, which can be used with other IDEs. I use Xcode because I own a MacBook, but I tested the set of makefiles successfully with NetBeans.
Adding another platform only requires writing a specific makefile for it. As at today, Arduino 23 + 1.0x + 1.5x are supported, as well as 6 other Processing-based Wiring-derived IDEs: chipKIT MPIDE, Digispark, LaunchPad MSP430, FRAM and Stellaris, Maple, Teensy 3 and Wiring. Which is next?
The dedicated website includes
Check the thread Arduino on Xcode Project — Official Thread on the Arduino forum.