I'm having to use Muster in my new job and finding it pretty stable. Previously I have set up and run render farms in several companies using Smedge 2, but that version is no longer supported by Uberware. This is a pity, as I mostly found the UI and methodology to be very simple, intuitive and reliable. I have a small home farm of six machines running Smedge 2 and will not even consider changing my render manager as long as Smedge 2 will run on my OS and run the rendering software (exclusively Maya). I always found the Uberware guys to be very helpful.
Muster seems pretty solid in terms of getting the rendering done without problem. The problems with Muster are mostly with the UI, which is horribly designed both visually and in terms of functionality. There are numerous annoying quirks to it, including it assuming you are always rendering from the "scene" folder in the Maya project structure and filling out fields accordingly whether you want it to or not, not remembering the last locations you visited meaning you constantly have to navigate back again, a jumpy and glitchy job submission panel that you have to be VERY careful with to avoid settings changing without your realizing, and probably worst is the unbelievably stupid need to set the starting output frame number with every single job.
But, honestly both of these programs will probably suit your needs if you take the time to set up your network properly. This is key to getting any render farm to work properly.