I have recently bought STM32F429I-DISCO (or STM32F429I-DISCOVERY) board from ST. Unfortunately, as far as I know, it is not yet supported by any free IDE. I am trying to compile the project under CooCox (with moderate success, the test applications are working but the main payload with FreeRTOS is not). I was using ST-Link Utility for programming the FLASH memory so debugging was not possible. To enable debugging the application under CoIDE a dedicated FLASH programming code had to be prepared.
I have managed to adapt the sources of FLASH drver provided by CooCox for the STM32F429I microcontroller. I enclose the modified sources and binary driver. For quick and dirty installation, you can just copy the ELF file into the 'flash' subdirectory under your CoIDE / CoFlash application and point it in the project settings (last tab). I have verified my modifications by downloading the example application from ST to FLASH. Using the driver I am also able to download my compilation to the microcontroller and debug it. I cannot guarantee it is 100% correct but at least it works for me :-)