I found a new Minecraft SMP called Dying Light SMP and it is meant to be serious and long term with players who actually stick around.
It is using a Strength SMP plugin so your gameplay changes based on what you do. The idea is you get stronger over time and try to survive longer while making your own story.
They are doing applications to keep the server active and not full of random people who quit fast. Expect player driven alliances and conflicts with a serious but still fun vibe.
The server is launching this weekend on Friday 27th of March at 7pm GMT+0 and they say day one is a big deal.
