The best microcontroller development environment is a very subjective thing! This is my subjective opinion, which is coming from the perspective of a professional who designs and develops consumer products.
I pretty much work exclusively with Texas Instruments tool chain for ARM Cortex M4F Microcontrollers (aka Tiva C Series). So that means Code Composer Studio IDE, which is an Eclipsed based IDE. It does the job, I do miss the auto-complete/intellisense feature which you find in IDEs like Microsoft's Visual Studio and Apple's Xcode, also the lack of a Macintosh version is annoying (but something they are looking to correct at some stage). But it does provide the low level stuff that you need to access sometimes, assembly stepping in debug mode, access and ability to change memory directly etc.
One other thing to consider, is not just the IDE, but the SDKs and other environments that are provided. I have recently begun using TI-RTOS (Texas Instrument Real-Time Operating System), which is available for free. working with an RTOS makes life so much easier, and to explain how is more a topic for another thread, but if you want to find out more, check out this link -
http://processors.wiki.ti.com/index.php/TI-RTOSTI also provide TivaWare which includes examples, drivers and code for just about any peripheral, including USB, Wifi, ADC/DAC, Timers, Graphics, Bootloaders....and whatever.
Another option for developing on TI ARM if you do not want to develop in C, and can do without inline debug (not something I could ever do without, but lots of Arduino projects are developed in this way...you Arduino developers are a patient lot!) is Energia (
http://www.energia.nu/) or if you want to develop on Macintosh and want auto-complete/intellisense then check out embedXcode (
http://embedxcode.weebly.com/)
And hi everyone, my first post in this forum.
Glenn.