Somebody once suggested to me that this could be very hand for the reproducible builds folks. I'm sure that now that we're out in the open, lots of people will suggest great applications for it.
My favourite application for "deterministic computer" is creating a cluster in order to have a virtual machine which is resilient to hardware failure. Potentially even "this VM will keep running even if an entire AWS region goes down" (although that would add significant latency).
Disclosure: Antithesis co-founder.