eXP doesn't contribute anything to the stability of this system over a regular XP system which is set up correctly and left alone. The stability of the system will depend on the automation hardware on it. The benefits of eXP are smaller footprint, quicker boot times, easier to put on a solid state disk because you can strip out some stuff you don't need, less memory usage if you strip out stuff, etc... It also has a lower per-machine price if you are moving it in some reasonable quantities.
But the actual use of the machine and OS requires application software that targets the job you want to do. If that isn't stable, then the other stuff is irrelevant. You can't destroy the OS image or the application image, since it's on a solid state disk, and you can always just reboot it and you know it'll come back up OK (modulo any configuration data that you can change and might be able to hose.) But if the application software crashes, then it crashes and it will do the same on XP or eXP.
The big thing is that you have to limit disk activity if you want to have a long lifetime, because the solid state disks do wear out. Each byte position has a limited number of writes. The disks are smart these days and move data around to spread around the wear, but if you (for instance) log to disk, and you have some bug that just starts logging rapidly and it goes on for a month, then you could put some serious wear on the solid state disk.
We will also offer an eXP system, but we are going to start off first with a standard disk-based system, in the same system that we will also offer the eXP version. That way, we can get some experience in a less hard-wired system that can be more easily upgraded in the field as we work out the configuration.