Hi everyone.
Apologies for the delay of my response, but I have been a bit bit busy over the last few days.
To the point: I have tested the CM11 Nightly (the initial CM11 Nightly release) on the S2 (i9100), and can confirm that it is very stable. Battery life is great, and the experience smooth and refreshing. Overall I have only had two minor issues thus far: the first was a minor issue in WhatsApp, where I cannot clear conversation history for group chats - individual chat works fine. The other was the local profile account, which I cannot configure/ setup. By this I am not referring to the profiles feature/ service, but to the local profile that configures your contact card, on your local device.
I would definitely recommend that you guys try CM11 - it is an absolute pleasure to use. Let me know your thoughts and experience on using CM11 if you have used it.