I know two companies running running openshift on Mesos. The reason modern Paas aren't enough, is the factat some scale you're not just running web services. But also rather complex data pipelines involving distributed data systems like kafka, spark, cassandra, etc .. and a simple paas has issues handling those workloads. That's where Mesos shines. As for the user value, I consider having an uptime system, providing reliable and intelligent service based on data processing, by efficiently using your resources is has an important business value.