Hello,
The cPanel release 11 which is also referred as EDGE is used for testing purposes and thus you shouldn't expect a stable behavior from it.
We don't inform about cPanel 11 because it is still in development.
Since I asked the first time for a solution nearly a year has gone.
Is cPanel 11 now stable and recommended for installation/upgrade ?
cPanel 11 is rather stable now and we use it on our servers installed recently. It comes with some significant changes to mail and Apache build systems, but they allow to do more customizations and optimizations to the software installed on the server.