Question -- pros and cons of a realtime OS

I think you need to be very specific on what you consider "realtime" and what you consider "realtime" requirements before asking the question.

I am asking for fairly general observations and peoples opinions and experiences in the form of "pros and cons" to realtime systems. The matter of needing a supposed realtime system, like QNX or something, is a different subject based largely on the previously mentions pros and cons and the application.

That said, I have already pretty much decided my position, but would like to see addition points of view to either further justify my position or force me to rethink it.

If you use RTAI with Linux, there is no cost component, no device driver complexity, and the support is pretty good.

In some versions, you can run your code in user-space.

cheers, Rich.

For robotics, option 3, neither, ie, your-realtime application with whatever integrated OS features it needs.

pros: better realtime performance and lower latency simplified hardware and sofware design, i.e. focused reduced cost in development, debugging, and licensing simplified device drivers

cons: knowledge required outside of realtime OS and general OS programming