IIS Application Pool - Maximum Worker Processes

Has anyone changed the Maximum Worker Processes on their REST and SOAP API server from 1 a greater number.

As far as I can see, changing it from 1 to 2 spins up another w3wp.exe process, so *should* add to the performance of the API (providing there are free resources).  The session state isn't shared between the worker processes, but I don't think this matters, as we can run multiple REST/SOAP APIs which are independent of each other.

Thoughts, suggestions, horror stories?

Thanks

--Wayne