I already use CoreOS/etcd/fleet to manage a cluster of apps and services. What does Deis do that I can't already? Does it have solid automation for service disc

I already use CoreOS/etcd/fleet to manage a cluster of apps and services. What does Deis do that I can't already? Does it have solid automation for service discovery and the like? I want to be able to quickly add and remove nodes depending on demand. Does Deis make this easy?