The recent report on RTOS capabilities of VxWorks, WinCE 5.0, MontaVista Linux 2.1 is a nice comparison of these popular platforms. For WinCE 5.0 in particular, it was stated that Platform Builder - the choice for creating BSP is not reliable. I don't know what led the authors to this conclusion, but I disagree with this. It may be diffcult to find out a mistake by looking and output windows error messages, but PB is quite stable (though somewhat slow at times) and I have used it extensively for quite some time now and I don't think of a better environment to get started. In addition it also enables you to build entirely using command-line if you wish. So GUI/CLI is a matter of choice.