Hi!
Arduino is fine but the IDE lacks many features I enjoy with Xcode.
So I tried to write my Arduino code on Xcode.
After extensive research on internet, I've obtained a Makefile that works!
I tried Nick’s modified version of ArduinoOnXcode template plus all the following hints:
- on Makefile, set values for the MCU, upload speed and the protocol according to file located at Applications/Arduino.app/Contents/Resources/Java/hardware/arduino/boards.txt
- on Makefile, add $(ARDUINO)/WString.cpp to line 73 before $(ARDUINO)/Print.cpp
- on Makefile, change line 67 from PORT = /dev/tty.usbserial* to PORT = /dev/tty.usbmodem*
Here are two projects running fine 
on my Arduino Uno with Arduino 0022 IDE and Xcode 3.2.5 on Mac OS X 10.6.6.
I started with a small project, the famous LED blinking and "Hello World".
- Arduino-1: very basic
- Arduino-3: with a class for the LED
They are built and uploaded to the Arduino board successfully, but they're pretty basic.
Please refer to attached files.