The big claim to fame for the IBM Z series is supporting hot failover so the workload will never go offline. For web tier or app tier, where you want to scale horizontally anyway, it's pointless overkill, but for relational databases that have a maximum of one write master, you could make the argument that it's valuable.

I'd be interested in reading the perspective of someone actually deploying it though.

Honestly, it just works. I can do a docker image that runs on aarch64, amd64, and s390x. For the SpringBoot apps - the hardware is rock solid and far more important, cheaper and under provisioned than the other 'standard' compute for those who have piles of legacy systems. OpenShift on zSeries is not a lot different than Intel based boxes.

I wonder if IBM Cloud runs it on s390x.