Beside mbed online compiler and closed source Keil, What is the best open source IDE for Arm software developer ?
I do not see the arduino_ide as a good starting point for a professional, even for a student who wants to learn to program Arm, well actually I think it may even be that the Arduino is a good starting point for anyone start with diy or professionals from other sectors such as fine arts, architecture and music projects.
But if you want to become a good programmer, the level of processor or microcontroller, which is interesting since start of more complex place, of course a tool to assist in some activities is important, even with the complexity of eclipse I find it a good tool for those with time to worry about details, plus the Eclipse's ready solutions like the DS-5, the choice of GNU Arm plugin, as suggested by ilg also is a good choice, but there will be a learning curve for details regarding Eclipse.