We are rolling out session affinity for the routing/revproxy layer for RUN@cloud applications. Session affinity means that when a user is routed through to the backend server - they stay with that server as long as possible (makes it much easier for some frameworks to scale). If you don't know what it is - you probably don't need it !
If you are interested in testing this out in your account - we would love to hear from you.
Currently this requires having your own SSL router setup - as per wiki.cloudbees.com/bin/view/RUN/AppSSL. If you have that and wish to try session affinity - raise a support ticket with the name of your router that you wish enabled and instructions will be provided.