Mesosphere DCOS is a platform built on top of Mesos that abstracts away your underlying infrastructure for containerized applications as well as for applications you don't want to run inside Docker. This may be overkill for more modest deployments, but we're beginning to see successes with both the commercial and open source versions. We particularly like that it facilitates portability between different cloud providers as well as dedicated hardware, and that for containerized workloads you're not tied into one container orchestration framework. Although upgrades can be a little more complex than we would like, the overall stack is stabilizing nicely.
Mesosphere DCOS is a platform built on top of Mesos. It provides an abstraction over underling machines, giving you a pool of storage and compute that allows services built for DCOS to operate at massive scale (Support is already there for Hadoop, Spark and Cassandra, among others). This is probably overkill for more modest workloads at the moment (where plain old Mesos could still be a good fit), but it will be interesting to see if Mesosphere starts trying to position DCOS as a general-purpose system.